Not why the addiction, but why the pain.
The difference between passion and addiction is that between a divine spark and a flame that incinerates.
We may not be responsible for the world that created our minds, but we can take responsibility for the mind with which we create our world.
It is impossible to understand addiction without asking what relief the addict finds, or hopes to find, in the drug or the addictive behaviour.
In the real world there is no nature vs. nurture argument, only an infinitely complex and moment-by-moment interaction between genetic and environmental effects.
Autonomy is impossible as long as one is driven by anything.