They didn't start as a standalone business (specifically Tesla and EA), but they're going to have to figure out to be a sustainable business.
Sure they can use government money to help build out a network, but the network itself needs to be sustainable. Can they be sustainable by themselves (low overhead as they're automated) or does it need support of a store selling $5 candy bars, and $5 bathroom access?
As to Tesla:
You keep saying they are often broken, but that's not the case with Tesla Superchargers.
Tesla chargers were never really free as the cost was added into the cost of the vehicle. I had free supercharging for my ownership period in my Tesla Model 3 Performance, but gave that up for a $5K check from Tesla. This was known as the Fred incident when Fred complained about the cost suddenly going down and then Elon explained that free supercharging was removed. So if a person was willing to give up free supercharging they would get a "refund".
As to gas its pretty well known that Costco gas is on average 35 cents cheaper which can add up to some significant savings. But, obviously that's a membership thing that's sustained by everything else Costco sells.
Tesla's approach was sustainable, building the extra costs into the price of the car. As they move to trying to recover costs or make a profit, it does need to be sustainable in a different way, but not like a normal business or gasoline business. Tesla can readily tolerate having a network that loses money or breaks even because it truly is the case that the SC network makes a Tesla by far the best -- some would say the only -- car to road trip in. And lo, 3/4 of EV sales are Teslas, and this is one of the components of that success.
I only got 1K of free supercharging (but earned 4K miles more from referrals.) Still have a few left due to lack of trips during Covid. Unlimited charging led to use of SCs in your home town, which is not sustainable. (Tesla could have and should have offered free supercharging only >100 miles from your home.)
In those early days, Tesla didn't even have SC in the major cities, so you didn't use it near your home. Later, they built up the network there, and started supporting the people who can't charge at home or work. The right solution for that is to get those people charging at home or work, and that's where all laws and subsidies should be directed, not so much at interstates. Maybe a subsidy for chargers in regions where there is no other fast charger for 100 miles, that could be handy.
But this is the problem. Most people have a $1/gallon "gas station" in their home. The EV charging business involves opening up a $4/gallon gas station and hoping to sell these folks gasoline. Not going to happen except when they are away from home and have no other choice. There is a business of serving the people who have no choice, but it's not the big business people imagine.
Even on the road we will see most hotels putting in charging over time. Either free (with hotel stay) or hopefully priced less than fast charging. That eats away a large fraction of the fast charging market. Only people going >200 miles use fast charging at all, and those going 400 miles use one fast charge instead of 2. The few who go >400 miles use 2 fast charges instead of 3.
It's just hard to make a business there. Not like gasoline which is pretty much all the same, and nobody much cares where they get it. EV charging has to come at a place I want to stop for 30 minutes, ideally with food (but I only want that at lunch or dinner) or maybe shopping but who wants to shop for 30 minutes 1-2 times/day on a road trip?
So people put in the stations to get subsidies but they don't get motivated to maintain them. Tesla does maintain them, but some still are broken but their strategy of large stations with >8 stalls means a broken stall means very little, at worst a rare slightly longer wait. A broken stall at a 2-stall station can ruin it.
