Comment by hypfer

Just throwing more people into the same small space doesn't necessarily mean that they suddenly start interacting with each other more.

In fact, the opposite can happen, where investment into local social community building stalls completely, because why even bother? Why would you listen to ramblings you do not really care about when there is an infinite supply of new people that don't in this very moment?

That's one mechanism. There are many more.

Urbanization is good on paper, but has many shortcomings. Hypothetically, it should be the most efficient and best solution. That hypothetical just leaves out how humans actually work.