I spent hours (? months if you add it up) trying to figure out why. I suppose it did me no harm in that I am a lot more informed, compassionate and empathic because of the knowledge I picked up. However, what really helped me was to realize that the "why" made no real difference to the situation. Unless and until he started to ask the same questions with rigorous honesty, the situation wasn't going to change, because I had no control over whether he drank or not.
The "why"s that really helped were the ones I asked about myself.