I think what people need is not objectively measurable. If they only use supercharging for 1% of their trips, you could say they don´t need it statistically. However, if they feel they need it, they´ll base their buying decision on it.
The question is: do you offer people only what you know they will mostly use or what they feel they need? I would go for the latter. I am not saying build a swapping station at every supercharger. But like at the 10 most used ones for long distance travel wouldn´t pose too much of a financial problem and take away many peoples fears (as irrational as they may be).
How often do people need to go 0-60 in 2.8 seconds, or over 200mph? Should probably buy a car which can do those things, just in case, right? Only thing is, they're all a million dollars.
You can offer people "what they feel they need" - 400+ miles, apparently - and make a car which is lousy or too expensive, or both, which by the way we've heard Elon and JB say many times because it's true, and it wouldn't sell very well at all. If Tesla had offered a Model S starting with 400+ mile range, costing twice as much base and weighing 5600+lbs, do you think we'd all be talking here right now?
The auto industry has spent plenty of time designing by focus group. They get a bunch of people together, ask them what they think they want, and then make a Homer-mobile designed by a clueless public. At some point someone who knows better needs to step in and say "no, we're not doing that, you guys don't know what you're asking for."
Wild fantasies about what people think they want and what they actually will ever use need to be reconciled at some point. Which is where we reach a cost equilibrium between what people would like to have and what people are willing to pay for. Right now, the Leaf doesn't even have 100 miles of rated range, and has quick charging capability but not quite so quick, and yet it's the best-selling EV in the world by quite some way. Clearly much of the public understands that 100 miles plus quick charging is suitable for their needs. But the same 2-3 people, who inexplicably spend so much time on an EV forum, are constantly talking about how unsuitable EVs are for the general public because most people couldn't possibly get along without a 400 mile battery. And having these sorts of "advocates" sure isn't helping anything - it causes people to write off the entire idea of EVs, Tesla or otherwise, before even giving them a second thought, which is why the ICE industry pushes range and recharge times so hard, constantly reminding consumers of them. And some of us happily oblige. "With friends like these..."
Tesla is certainly not going to sell a million Model 3s by 2020 if the general public continues to be led to believe that 200 miles isn't even enough for a minority of their driving.