-More natural settings shown to improve mental health
-"neighborliness" scales inversely with density to a point - less neighbors means you're more likely to get to know them, while with more people there are too many so the crowd of people gets depersonalized to a degree, because 50 neighbors are too many to keep track of.
-you don't have to go to some crowded city park full of garbage when friends have yards with their own stuff like sandboxes where they can have some privacy from for example sheltered city people or park cops freaking out over the kids having nerf guns
-other activities become more feasible like bike riding (I wouldn't feel good letting a kod bike around NYC), ATV's, fishing
-more outdoors setting prevents aesthma
-safer setting for the kids overall
Your concerns just don't work oout that way in my experience. I was in single-home-only towns as a kid and there was no problem playing with neighbors or anything. Even when houses are a mile apart it's really not a big deal just being driven to them.
And since when do kids want to attend classes?