Since short sleepers are a tiny percentage, the traits in combination must not lead to more offspring surviving very often vs a regular human.

It might make a difference for animals, but we evolved in a society where we help each other and work as a group. Doing this probably means that less desirable traits stick around.

Take myself for example. I don't have wisdom teeth and I don't get cavities at all. You'd think that would be a huge benefit since bad teeth was a big killer in the past. But no, people like me are a minority. Apparently perfect, long lasting teeth are not a major competitive advantage.