We were dependant on our parents to do anything or go anywhere that was more than a few blocks away. No infrastructure for biking existed worth talking about. Sidewalks were sketchy; no one expected pedestrians. Visiting friends was
hard, and depended on parental coordination.
Any sort of outing was a Big Deal; kids had to be wrapped up and put in the car, then we all had to trundle off somewhere, then the reverse had to be put into motion.
A transit system in a dense urban area makes these issues go away.
Slightly location dependant - there were no museums of quality[0] within hundreds of miles; same for zoos, libraries[1], symphonies, operas, plays, etc. Density drives tax base and demand; any reasonable urban area has all of the above.
Suburbs, as a common rule of thumb, strive for conformity and blandness. This has held true since the white flight era in the US[2]. So you wind up with really crappy aesthetics, and uninteresting options for engagement. A very common result is the alienated suburban teenager bored out of their skull. We were, to greater and lesser degrees.
Now, as adults, we both recognize several serious problems with the suburb/exurb system in the US.
1. It's not sustainable economically. You have a huge infrastructure system on a low density population; hard choices start coming out to play because of the cost of maintenance, which generally was capitalized by developers, but the opex is borne by the government; local politics in the US has evidently generally shifted to anti-tax Republican demographics; with fewer people supporting the burden, issues come out to play. So the net result is life is getting worse there.
2. It's not environmentally sustainable. Efficiency rises significantly as you start densifying the region; new services become possible at critical masses - one of the big ones is transit. This drives pollution down, decreases oil use, etc, etc.
3. It promotes closed-mindedness; without having to deal with the breadth of humanity, you don't have to cope with all of the reality involved, leading to really terrible policy decisions. Forcing contact with The Other and humanizing them tends to work out better in the long run. Referencing current politics: https://twitter.com/nycjim/status/687997269258407937 . NYC's great strength is having to deal with other people.
Anyway, if you take some time to look carefully at the "new urbanist" movement, these themes are repeated over and over again. It's not democrat, republican, libertarian, or green; but it recognizes many of the issues those viewpoints present. I'm not ashamed to say that I'd rather live in Manhattan, NYC than in any arbitrary suburb I know of (Now, if I could afford that in a residence I could raise kids in... :( ).
[0] Local History Museum is what was available.
[1] Less of a problem as a young child, much more of a problem as a teen.
[2] Note that "urban" is often an appellation on something meaning "black people". I wouldn't actually call suburbs racist by design, but I would invite quiet contemplation of race and environment in the US.