Note that by good transit system I mean one where you never check the schedule because the next bus/train is never more than 5 minutes (that is a maximum time). By good transit I also mean a system of transfers to express service so you can get to more distance places quickly. Nobody in the US has a good system (NYC's subways don't even come that often!), but there is no reason we can't have that, and some places in the world do have it (at least for a few).
There's no logistical reason, but very few municipalities have the density to support that kind of frequency (via fare revenue), and taxpayers (especially in the US, but in other places as well) don't want to pay for all that unoccupied space on trains and buses.
I'm not saying that's a universal truth. There are a few places that do have the density to support that. And there are a few places that don't, but local residents are happy to pay more in taxes to get that kind of frequency. But most places are not like either of those things.
If instead you would accept that you can wait up to five minutes, and "other people" are nice enough and so you can share a space with them - we could have a nice transit system.
The five minute time I used above is not arbitrary. While there is some debate on the exact number, 5 minutes allows for a lot operational things that are really nice.
You can see how that viewpoint might be received in a lot of places nowadays, especially blue-collar places that rely on that type of work to still be available and not farmed out to some AI bots that will manage to also kill some of us in the process (but in smaller numbers compared to what our fellow humans would have registered, that's a relief).
