
Various reasons. If I was presented with a series of women who wanted to date me (that’s how we know this situation is hypothetical by the way.) I wouldn’t make my decision on looks alone. Personally, mutual interests, mutual attraction, agreement on key philosophical issues are all important to me.
Also (as demonstrated in these comments) people have their own issues. They could have a personal problem with pretty women, or they could be intimidated and think they’re out of his league. Or they could just be looking for a hookup and think they’re more likely to get that out of a less attractive woman.