Count me among those who think there is very, very limited value in trying to figure out "why" an addict does anything. Because the answer is pretty much always "because he/she is an addict."
I was raised to believe that knowledge is power, and I wasted a lot of time and energy trying to figure my AH out. Talk about a lesson learned the hard way. Now my message to my children is that it can be helpful to understand why a person might be acting a certain way, but it's not something to agonize over. And when you're dealing with someone who, for whatever reason, isn't rational, there's no point in trying to understand at all.