It is one of the top destinations because of all the tourists that want to come to the country where prostitution is legal.

If you walk through the red light district of Amsterdam at any given time of day there will be tourists packed wall-to-wall and relatively few locals (they are mostly on the 'supply side').

If every country would legalize prostitution the draw of this would be greatly reduced and Amsterdam would lose some tourist income (I'd be more than happy with that).

Drugs same thing. I don't know any dutch people that consume on a regular basis but almost all the tourists that I know and meet going to Amsterdam can't wait to get stoned.