Are they bad for human health compared to other ways of living like rural or suburbs? iirc rural people get the least amount of exercise because you just sit inside all day.
when we lived in the suburbs my family and i spent way more time inside than we do now in a rural setting. i think maybe you got mixed up. rural people are generally very active.
It would be an insane amount of roads, cabling, water pipes, etc.
Cities are bad for human health, but good for the environment.