The reason you go to kids' birthday parties because your child was invited and they're too young to go alone.

You can socialize and you kind of have to, but they've probably invited every classmate from preschool or whatever, so there's 20 people you probably haven't met before, have nothing in common except having kids the same age, and will probably never see again (except maybe at the next birthday party). And often the parties are held in a McDonalds or something, so catering is chicken nuggets and shitty cake with a Paw Patrol motif.