There's some observational bias at play. You notice the cases where the guy (usually) has "outkicked his coverage" and you may notice the very attractive singles and wonder about it. You don't notice the plain singles or the perfectly matched couples, but you notice the woman in the red dress from the Matrix.

Second, some people make a conscious decision to have a stable relationship. I'm not saying it's 100% choice, but it's well over half IMO. I sought [and found] a partner who came from a stable family, who was educated and valued education, who wanted kids, and who wanted a stable relationship. Did that contribute to me being one of "those people"? Probably.

Since there are two sides to the transaction, the number of people marrying more attractive people is exactly equal to the number marrying less attractive people.

I didn't cover ugly w difficul personality and beautiful w good personality, hence the disparity.