Why do nice guys have such a distorted definitions "nice"?

Nice guys often seem to think that being nice is either a 5 minute process which gets women to dispense sex OR they think that being nice involves being over-the-top nice, selfless and even boundary-less, forever to get sex.

We already understand for the most part where the drive for sex comes from, but why specifically do they have such distorted definitions of what nice is.

For me I think most well adjusted people that I identify as nice are usually very casual with some presents here and there (but not always); complements are infrequent, but sincere; for the most part, it's just being polite and neutral to most people, and not taking offense to often (but still drawing the line at intrusive behavior).

Why do you think nice guys have such a weird definition?