I never understood why people take it up either but I had a friend a long time ago that tried a couple of cigarettes on a night out (the usual, out for a drink, people were smoking so he tried it - it was a long time ago when smoking was 'normal'). Anyway, months later he started lighting up and I asked him what he was doing ? He said he just couldn't stop; I was incredulous and said but you just had a few draws on a night out how does that work? He was adamant that the addiction was immediate and there was nothing he could do to stop.

Some people just seem to be wired differently and even a small exposure is all it takes. I think other addictions to [illegal] drugs are the same - smoking has a little less stigma since it is legal (but's it's certainly not socially acceptable like it used to be 'in the old-en days' when I was younger).