Tough to say. I agree night clubs tend to attract certain types of people, but that doesn't mean that 100% of the people in there are of what @Andrew0409 and OP have described. I'm sure some people that go just like to get dressed up and have some fun.
For example, you got the guy who's wing manning for his best mate or the girl to make sure that her bff doesn't end up in the wrong place with the wrong people. I can't imagine those two kinds of people, who put their friends enjoyment before their own, are not marriage material.