why the hell did they guys act like this? Give it to me straight up! no wishywashyness :)?

So I've been told by everyone that I'm beautiful, guys ask me out/check me out all the time etc.
At this party last night, when we were walking in, two guys that soberly normally check me out were like NEXT, NEXT to me and my friends as we walked in. Guys who when they're sober, say that I'm pretty proceeded to dance on not cute girls, and completely ignore me. Why do guys act like this at parties? I'm just curious..thanks!