I've been thinking about this lately; why have I drunk alcohol once I realized it does nothing for me?
Here I think are mine:
Someone told me I shouldn't
I wanted to prove nothing bad would happen
It's a way to avoid responsibility
Wanting to prove I don't like it
Curious on yours, what you think about to, and maybe in this or a different thread we can look at why.
Grateful for you today.
Fear. That's an easy one for me! I was scared to death of life and the past and the future. Alcohol took those fears and pushed them down until they re surfaced as anger.
That's my reason. Foolish? Heck ya!
Great topic BTW!
It's so weird right? I mean there is no reason, but we have made reasons or excuses. Society doesn't help with all the brainwashing.
Ask the Jaywalker from the Big Book.
It’s the “sense of ease and comfort that comes from a few drinks”
Others drink with impunity, I cannot. It doesn’t really matter why I have the disease of alcoholism, I just do. I cannot drink like other people. It is a “physical allergy coupled with a mental obsession”. All I concern myself with is the solution 
I wouldn’t spend too much time on asking “why”. The fact is you’re an alcoholic and it’s a disease.