Why do people joke about hating their significant other?

It's boomer humor. Ive only ever heard older men make those jokes

I don't find that funny but it is their relationship. They set the bar for the acceptable humor. I am an outsider who lacks context.

It is odd but I've always found it rather affectionate it an odd kinda way 🤪

Its normally older people.

There is always some truth is just kidding. If you hear a woman saying things about her husband then you know she is up for an affair.

Yeah, it's kinda shitty. I mean, why get married if you don't get along well?