I'm a hobby guy and I don't do or like any of that. But it seems most beaufiful/sexy girls do.
IS there a reason why?

Actually, you just focus on the sexy beautiful girls who have fun in those clubs or party, so you have the misconception. Maybe you should try to find some un-pretty girls in party or find some hot girls in library, you will dispel your misconceptions.

Most of those girls crave attention, like to get all dressed up and strut their stuff. Where better than a club? Lots of guys to give them the attention they crave.

Well to me, there are a lot of sexy girls in the world in the library, post office, or even in the government offices... They are all sexy one way or another, but they just don't want to show people that. Since meaning of beauty is in the eyes of the beholder, if you think sexy girls are girls that wear tight , scanty clothes, then yes, they're all in the clubs.