After 20 years of living there, (and 3 visits in the 80's, when I was 20/21), I speculate that it's often the 'unholy-trinity' of booze, illicit drugs, plentiful supply of easy-to-get tarts????, that puts some guys "off the tracks". If the same things were as available in their home countries they would have the same effect.
Although as you say, women are the thing. also the fact that for many of us our experience with women there is of a 'transactional-nature' , they wouldn't give us a second look, if not for money.