It's not necessarily self control. Responses to alcohol are significantly influenced by genetics.

Even if everyone had the same level of self control, some people would still tend towards teetotal behaviour, others would develop alcohol addiction.

There was a study proving a link to one specific gene in mice a while back:

http://www.ncl.ac.uk/press.office/press.release/item/a-gene-...

Human responses are more complex, but there's enough research to suggest a strong genetic component in problem drinking.