I'm not sure it really matters much Amby. I desperately searched for a reason as to "'why" i am the way I am, but in the end it it really doesn't matter. I simply AM an a alcoholic, and comparing myself to others did not help solve my problem.
The symptoms you experience as an active drinking alcoholic can get progressively worse over time too. I personally had pretty much no withdrawal symptoms at all if I tried to quit earlier on in my life. Fast forward to the last time I quit and I ended up in the ER with dangerously high BP and heart palpitations.
Another thing to keep your eye on is that the "why" quest can also be your AV/addiction trying to convince you that you can solve "why" and somehow return to normal drinking. I fell for that one many times too unfortunately.