On a larger scale I think it's _a_ factor, but not the only factor.

It's partly a numbers game. There are definitely amicable cul-de-sacs but if you are in an apartment complex there's 100x more "neighbors" you could interact with.

Suburbs also come with the tradeoff of driving, at least in America. It's a lot easier to socialize when you can put on some flip flops and walk to a friend's place or an event than it is to drive.

It can be hit or miss in either case, and there's socioeconomic and cultural forces that make real world interactions more scarce. If more of my income goes to rent and inflation is too high why would I burn through money on going out when I can stay home and watch a show or be on my phone