Because they're incredibly slow and you'd need a giant facility to accommodate what even a tiny 4 pump gas station currently does? I live in Seattle and there are tons of Teslas, but the nearest Supercharger is way out in the suburbs at a mall so you can do something with all your waiting time.
I think the number of spots you need is actually similar. A car will occupy a spot for much more time, but it will need it much less frequently since it’s only necessary for long trips.
That’s why your nearest supercharger is out in the suburbs: it’s for travelers, not locals.
We're going to need a ton more spots, it only works now because almost no one has an EV and those that do are self selected to people who can charge at home. Somewhat ironically, EVs currently work best when you live in the suburbs and commute into the city. If you live in the city you likely won't have a garage where you can charge. Even if you drive to work and your work has parking and your work parking has EV spots at best there will only be a handful.
