Honestly, I think the main draw of nicotine for a lot of people is... the social aspect. Smoker groups are their whole own clique, and it's not uncommon for a lot of them to feel a bit like outcasts in society otherwise. Smoke breaks allow for synchronized socializing as well as providing an "in", since everyone in the smoker group is, most commonly, a smoker.
My friends at that Norwegian school program I was in used to joke that I smoked the most of anyone at school, despite being a non-smoker. All of my friends were smokers, so I'd always hang out in the smoker groups and suck up that second-hand goodness.
It perpetually baffles me how people consider taking huge quantities of poison "fun".
Junkies are junkies.
I certainly don't plan on ever trying junk - for one thing, I'm a bit leery of needles, and if I somehow found it in smokeable form I'm sure I'd be much too fond of the stuff from the outset.
Well, it actually is smokeable. Also snortable, just as cocaine can similarly be smoked or injected. Russel Brand smoked smack, and talked about how he kinda envied the guys who could shoot it up, but he didn't know how and was also leery of needles.
Also, regarding endorphin highs, apparently Norway has something like a 14% incidence rate of unhealthy exercise addiction! So that's fun.
The drinking problem statistics are much worse though, and are the primary reason why booze is so heavily taxed and controlled... Which, ironically, is most likely just making the problem worse.