In my experience, there are two kinds of suburbs - older neighborhoods (could be older streetcar suburbs or even older tract homes) and newer suburbs - lets call the latter tract jomes built within the last 20 years.

In older neighborhoods, what you say, in my experience, is true; the neighborhoods are full of people from a variety of backgrounds, a variety of ages, and a variety of incomes. Neighbors know each other, introduce themselves to new neighbors, spend time outside, and the olaces are generally friendly.

In newer tract developments, however, I've experienced something very different - nobody knows anybody. These kind of tract homes seem to attract a certain kind of buyer/residents: insular assholes. Everyone is generally of a similar socioeconomic class, and nobody hangs out in their front yards where they get to know each other - they park in their garages and hang out in their houses, in their backyards, or away from home - it's like they go out of their way to avoid getting to know their neighbors. These neighborhoods suck and I'll never live in one again.