Simple answer.... because it's fricking amazing!!!!!
Long answer....
Tbh not many people initially like the taste of alcohol when they first start drinking... unless it's alco pops or some types of cider. But myself.... I really like the taste of a nice cold pint or a cool ale and the social environment of a pub.
However I have no idea why I insist on getting completely slaughtered every so often in rubbish clubs and bars that play music I don't like, that charge me £4+ to get in, only to buy overcharged drinks.
Then again rock bars/clubs, I really like, give me one of those and a drink promotion and I'll get slaughtered, have a laugh, dance, singalong etc..... like I did last night, hangovers are horrific for me though, roughly 3 pints will make me feel flu-ish the next day, 6+ kill me. Or get me on the vodka and I could make drinking a national sport!!!! Also pulling on a night out is never a bad thing! Also while I'm not gay, I actually find gay clubs to be really fun! If you're straight it's great fun of having a night out without that pulling environment.... though I did pull a girl in a gay club once.... but that was because we ended up speaking in the smoking area for like 4-5 hours and both thought why not.