That's a darn good question, and to think about it too deeply will take me to a place mentally I don't want to go. I gave the usual excuses like stress and rewards, traditional celebrations, time off etc....as to why I drank. But I think a big reason I drank was because I felt like I was a loser in life. I am not wealthy, I am not powerful, I have no kids, my business grew....then shrunk. I thought I was going to grow old living a very undistinguished and unremarkable life. Basically a poor childless drunk. And that may have come true if I continued to drink.
I personally don't think its necessary to know why, but that's just me. I try to always look forward and to find out why means I'd have to look back. I'm not the same Jeff I was 2 years ago and never will be. I don't need to look back, I know what it was like, I was there. haha.