I grew up in a mega city and I agree that cities are wonderful for kids, at least they were wonderful for me and my friends. I'd venture to guess that kids don't care. Cities or not, the world is just so much fun and exciting.
I don't know if suburbs are prisons for kids, though. My kids love suburbs, and they also love cities when they spend days and nights there.
It's not that parents falsely think that cities are bad for kids (it may be a factor for some people, of course), but that parents themselves do not want to live in a busy city. For instance, I have zero interest in bars or clubs. In fact, they are way noisy for my social needs. Instead, I just want to have walking distance to woods and shaded trails. And I want to have access to those large club houses that have full gyms and swimming pools and cozy libraries and all kinds of activity rooms, instead of those smallish ones in SF (probably because I'm not wealthy enough, but that's also my point). Or take Asian supermarket for another example. There are really not that many choices in SF or NYC. Even for the available ones, let's say H Mart in NYC, I really don't like the cramped space. I want to have those spacious walkways and shelving and big food court and etc.