Parents by necessity need to prioritize their kid. Hard to relate when you're single. So I understand why parents seek out other parents; they have a common talking point built in for an icebreaker.

At the same time, that very much is cultural. We think we need to raise children alone, and that's very much not the case in many societies. Good friends (even single) would be part of the family and help out with looking after or playing with the kids. Basically an uncle/aunt.