I understand if it's for Greek life, a small friend group, or if it's really crowded, but doesn't it just suck when certain parties act his way?
It's quite unfortunate, but imagine this situation:
It's a slow night and there's not much going on, expect for a house party. The house party only allows certain people in. Maybe it's to regulate how many people come and go, but honestly, it's just frustrating when this happens.
If I ever threw a party, then I'd allow anyone in, I don't care, unless if it gets too crowded or crazy, then I'd try to fix any problems. In the end, it's technically the underage drinkers fault because they decided to come. But, I'd still have to deal with a possible noise complaint.
Overall, we all like to have fun at college, but understand that some people don't like to stay in their dorms on a Friday or Saturday night.