It really doesn't taste that bad. I don't like lager or straight vodka (seriously, you're not meant to drink that stuff for the taste you know), but there are plenty of ciders that taste genuinely nice, and it's a lot easier to drink more when you're already a bit drunk (which is why people often end up getting smashed and throwing up... it's like an accelerator). Alcopops pretty much taste like non-alcoholic drinks, although I don't drink them personally.
I'm surprised it's such a ~mystery~ to non-drinkers why people drink, especially people who have never actually been drunk. It's quite fun. Especially when you're with a group of people who know how to have fun. Being very slightly drunk provides you with a pleasant effect without really damaging your health much, and drinking more than that is risky but sometimes it really pays off. It's a lot easier to make friends you've had a few drinks because you become more carefree, more confident and less judgemental, and people usually appreciate that. Sometimes you become a loud annoying **** and do things you regret - swings and roundabouts.