I get what you're saying. Having kids forces you to grow up and be responsible whether you like it or not :)

I believe the 'social privileges' refer more to things like "when are you going to have a family of your own?" and other prevailing attitudes that suggest that no one can possibly be complete without reproducing.

I've also heard it suggested that one cannot POSSIBLY be mature until they've had kids. And yanno, those of us without kids who do work hard for what we have (even if we don't necessarily have stunning careers) may resent that just a tiny bit.