^yeah, there's just so many reasons.
Oddly enough, I remember when I was about 12 I said something like "I'll never do drugs.".......Then when I hit 14 I stopped being a goody goody, changed completely! I tried pot because all my friends did it, and it didn't seem to fuck them up or anything, so I eventually tried it myself!! At this age I also started drinking lots and just being a bit of a rebellious teenager I suppose! So i dunno, for alcohol and pot, I think it started as just something to kill boredom and just simply enjoying the way alcohol made me feel, how it made a party back then, and jsut teh stupid stuff w eused to do like breaking into abandonned houses and having summer parties in them! It was also very much a rebellion thing though, that grew into the norm after time. Very routine. Just for the socia aspects.
But then I started doing e's, speed and coke, all the 'party' upper drugs, around about 18. I think the reason i started doing these was out of pure curiousity, but unfortunately I did end up doing it far far too much, and I became dependant on them for socialising and to fill a void or something......But despite that it did tell me a hell of a lot about myself. I learnt a lot.
Then came psychedelics......I think these will always be my favourite types of drugs. I only believe in doing them in moderation through my experiences with all the other drugs before that......The reason I do them isn't to boost my self-confidence socialbility or anything (They are the most powerful types of drugs, and shouldn't be fucked with basically!), it's purely a treat to trip every now and again...... Self-exploration and novelty I suppose! I hardly do any chemicals now, only when I feel like it. Which isn't very often. Simple novelty.
Sorry that was a bit long winded! But I felt there is no single reason why people take drugs. I just wanted to explain how it's evolved for me: ---> Rebellion/Curiousity--->Curiousity/Dependance--->Self-Exploration/Moderation..........and a just a general good laugh!!!