Here's an interesting theory: Alcoholism is a genetic trait.

After decades of breeding rats into two categories, drinkers and non-drinkers, found that 930 genes differed between the same breed of rats over the many years. While the new genes are not necessarily proven to promote an addiction to alcohol, the fact that there is such a variation is noteworthy.

Source: https://www.sciencenews.org/article/rats-offer-clues-biology-alcoholism?tgt=nr