Drinking does not make things more fun, that's an opinion not a fact.
You say you've asked teetotal people why they don't drink, why should they be obligated to answer you? Would you like it if they had a little mini rant about sobriety then asked why you were drinking? Or if a smoker asked you why you didn't smoke? Some people have different preferences to you. Doesn't give you the right to assume they're boring/from a troubled background/sick
I'm twenty, at Uni, and I go out regularly of various different places. I have as much fun as anyone else, my judgement isn't impaired, I can see my friends are okay, I spend maybe £7-£10 where they spend £30-£40 and I remember it the next day