Is it because they've probably been laid out by someone's mum? Or because they're always things that you wouldn't eat anyway, like breadsticks and mini sausage rolls? And because there's always loads leftoever that you imagine the host won't ever eat because they've been out for too long and might have been touched by other people.
I once went to a houseparty that had a laundry basket full of crisps. If a party wasn't lame enough already, the snacks will give it a pathos overload and I'll have to walk home.
I think if I was to write a short story about a party, I would write it from the perspective of the snacks.