You're speaking authoritatively but you don't even understand the basics of a lot of municipal train systems.

> they take up a lot of space that people can't walk on, that cars can't drive on, that isn't useful to park housing or commerce near

there are multiple cities that already have systems where all of this is true through various sections — Boston for example has the green line, which has rail embedded in streets that people often cross, cars drive on, and run center to streets that cars park on. Businesses near transit lines like this see increased foot traffic as people leave the train to walk home. People take groceries, bikes, furniture on trains... children use them to get to school, they're accessible the elderly and disabled. Many things that automated cars can not do.