It's true that most automakers don't want to build and sell EVs (largely because getting their dealer networks to push them is so difficult; also because infrastructure problems are hard, and the market is new - big, established companies are better at incremental improvements in existing technology than at major technology changes). In fact most of them have petitioned CARB and EPA to change the rules so they don't have to build them.
But the more interesting question is, why are the few companies that are trying - Nissan, GM, and apparently BMW - also not making no-compromise plug-ins?
I am pretty confident that these companies could build a good Tesla competitor; but I don't think they're trying because they are managing a whole portfolio of vehicles. Why bother spending a ton of money to create a long-range EV and infrastructure for an uncertain market when you already sell a whole line of gas cars that have long range? People that want long range can just buy gas cars, right?
GM, Nissan and BMW aren't trying to sell plug-ins. They are trying to sell GMs, Nissans and BMWs at the highest possible profit (and getting some plug-in credits helps them do that). Managing a portfolio is much more nuanced than a new company building a single car (and build their brand image at the same time), where the goal clearly has to be to make that car as good as possible. To sell a car from their portfolio, the large automakers first have to get customers in to their showroom. They won't go there unless they like the brand, so the companies have to maintain their image. They have to show customers something interesting to get them there; and then they have to sell a car...though it doesn't have to be the same car that drew the customer in. In fact, ideally they would sell their highest-profit car, which likely isn't a new model with a lot of new technology. They have to keep costs down or it doesn't matter how many cars they sell; they can't make every car the best ever.
GM built the Volt as a "halo" car. It is much like the Corvette - the point isn't to sell millions of Corvettes (though they do want to sell some to get them out there to be seen). The point is to show that GM has great technology and can build great cars, and get people in to look at the Corvette even if they end up buying a Malibu SS. The Corvette is a sports car that draws in customers that care about performance. As Bob Lutz has repeatedly said, the Volt was meant to show that GM could out-Prius Toyota, and get customers to think of GM as a "green" company. Because no matter what type of vehicle they actually buy, people prefer to buy vehicles from brands they feel good about. Different people care about different things, but brands that can make the most compelling sporty/green/off-road/safe cars have the best chance of drawing in buyers. GM's biggest brand deficiency several years ago was their "green" cred ("cred", of course, having much more to do with perception than reality). That's why they were running ads a few years back talking about how many cars they made that got over 30mpg. Consumers only buy one car, not a fleet, so from a direct sales perspective the ads made no sense at all. But what they were trying to do was to improve their brand image by getting people to think that GM was a "green" company. The Volt does a great job of that; it uses far less gas than a Prius and is much nicer to drive. But GM has bragged to their dealer network about how many people came in to see the Volt and then bought a Cruze. Halo in effect; even when Volt sales were very low, they were still selling GMs. They are expanding the Voltec line, adding features, lowering prices, changing the marketing - they are trying to sell more plug-ins. But the more important goal is to leverage the plug-in image to sell more GMs.
Nissan and BMW are of course hoping for some halo effect too by offering electric cars; that's a new thing that not many companies offer (at least not outside of the big ZEV states). According to industry surveys, Nissan's "green" image took a huge leap when the Leaf came out. But they seem to be going beyond halo, and shooting for "conquest" cars. Gas cars from different companies are all pretty similar; different models just have different price/performance/economy/utility tradeoffs (and some smaller brands consistently lean towards one end of the spectrum to give the brand an image; existing customers get upset when a brand introduces a vehicle that doesn't fit the image, though it usually brings in new customers). Given that they are selling near commodities in a saturated market, a key strategy to higher profits is to steal customers from other brands. Buyers are brand-loyal; so customers from other brands are harder to get, but more valuable long-term. Getting more customers increases volume, which is key to reducing fixed costs. Stealing customers from other brands is highly desirable. And that is exactly what the Leaf is doing (and what I think BMW expects the i3 to do). Nissan has bragged multiple times about the conquest figures for the Leaf. If they were really trying to sell as many EVs as possible, they would do what they do with gas cars - offer more styles, make them look as good as possible, make them perform better, and give them what everybody is asking for: more range. But they are trying to sell as many Nissans as possible, not as many EVs. They want to sell the EVs to draw in customers that previously would have gone to other brands, but they don't want to cannibalize sales of their existing higher-profit gas cars that already have great range.
This approach explains Nissan's marketing. They have long known from Plug In America advice and from their own research that environmental reasons are the last reason why people buy a Leaf. And yet they have continued heavy marketing of the environmental benefits. (As US production ramps up and their available volumes are higher, they are starting to focus on price; but that's an issue I may discuss elsewhere). If their goal was to sell as many Leafs as possible, they would have changed the marketing long ago. But they are looking to improve their brand's green cred, and to pull in environmentally-minded customers to the showroom where they can sell them any Nissan. The advertising makes sense if you are hoping to make conquests, rather than to change the industry with your new car.
I am expecting BMW will follow a similar path with the i3, and hope to pull in conquest buyers without cannibalizing sales of their existing models. (Although they might focus on the new technology rather than the green angle). That's why this BMW doesn't have the good looks of other BMWs. Of course, they also have to maintain their sporty brand image, so they can't release an awful car (this is why most compliance cars are still good cars; in fact most are hailed by reviewers as the best in the range - adding electric propulsion is the best thing you can do to a car, so you'd think the automakers would catch on). I've seen very mixed reviews of the i3, from very high praise to quick dismissal. I look forward to driving one myself.
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Edit: I want to make it clear that I'm not knocking the Leaf or Volt here (nor the i3, which I can't because I haven't driven). They are priced much lower than the Model S, and so expectations should clearly not be as high. Yet the Volt has had the highest customer-satisfaction ratings of any car for three years in a row. Leaf ratings are not far behind; while the Versa (a gas car the Leaf is loosely based on) is very near the bottom. The Volt and Leaf are very nice cars, and if I couldn't afford Teslas they are the only cars I would consider owning. They are just not industry-changing cars like the Model S - most of that is due to perceptions; the cars are great as the satisfaction ratings show, but many people don't understand how plug-in cars are used so they think they have many compromises that owners don't actually have to make. Even though they rank up there with GM and Nissan's best gas cars, they are not the best plug-in cars that Nissan and GM can build. To change perceptions and move the industry, we need the best. Tesla's role here is crucial, and that's why I've given them so much of my money when my wife and I would be happier with a Volt and a Leaf and a lot of leftover money in the bank. I am paying extra to help speed up the transition.