These are the only benefits I can see out of this. Although most people would prefer not to date someone less attractive than them whether they like to admit or not.
They’re more likely to be nicer to you and take an extra mile for you
They’re more likely to put out and please their better looking partner because they don’t want to lose them. They’re less attractive and they want their offspring to look more attractive than them, so they’re more willing to be nicer and take an extra mile for a better looking partner.
They’d tolerate your bullshit more
Usually the less attractive partner puts up with more of the bullshit. They’re more willing to put up with bullshit because they’re getting sex from a better looking person in return. Doesn’t it feel good when someone still loves you and tolerates/accepts your personality flaws?
You’d look more attractive than you usually do when you’re with them
The visual difference between you and your partner is evident. You’d look more attractive in contrast when you stand next to them than you would when you stand alone.
They’re less likely to cheat on you
They already landed someone who’s above their league, so why would they cheat?
They’re less likely to leave you
The probability of them finding someone else above their league is low, so they’re more willing to settle and commit.
The only disadvantage
Your kids will probably look less attractive than you, but there is a chance they won’t look less attractive than you. And people will try to tell you can do better which would result in insecurities.