Of note, but very minor compared to what I said above, I started because it would make me feel cool! It would help me fit in, and it would make me more sociable. Those things weren't true. I moved in to my own apartment for the first time and started having a glass of wine with dinner.. and it progressed with the boredom.. and my first relationship ending.. and with job loss.. depression.. more boredom. You get the idea. :P In the end I was clinging to it like a life preserver and it didn't make any difference, I was sinking. I'd never learned how to cope with life as an adult.
Now that I'm thinking of it, the addiction was secondary to the low self esteem, and that came about because of what I said above... and the quitting part goes in to that.. but starting, on alcohol specifically, and why did alcohol become the coping mechanism and the compulsion? 'Cause it was cool!