Most Helpful Girl
They're an easy target. They're less likely to be turned down by the drunk girl, they don't have to be charming or suave with the drunk girl, in fact they don't have to be much of a gentleman at all. They can put in minimal effort and have an increased chance of getting lucky. I personally think it's the amateur way (as a man who is truly good with women would prefer the sober girl), but those are the reasons why a lot of guys stoop to that.