First off, it rarely happens. Most people are looksmatched.
Yes, some women truly don't care about your looks or height, but they are rare enough that you'll likely never get to have one of your own.
You rationalize it by realizing that you don't know a single thing about their relationship except for what's on the surface.
I know several of those relationships.
In one of them, the dude has an apartment near campus and the girl is living there on his parents' expense. I feel like this relationship will end as soon as she's finished her degree.
In another one of them, the girl treats him like a doormat, goes to clubs regularly and cheats on his boyfriend. He takes it because she's the best he can get.
In another ugly man hot woman couples, they have been dating since highschool, and these relationships tend to last a little longer, but you don't know how long it will last for.
Also, when women say they see ugly men with hot women, remember that their standards are unbearably high, so what's ugly to them is objectively attractive.
I see ugly women with men hotter than them all the time though.