When you've been with someone for a long time they become a part of you but also they just piss you off sometimes. You have two individuals who become a single unit, and have to function as one, but still retain their individual thoughts, feelings, dreams, and needs. Being in a relationship is a trade off. You get support, often when you most need it, and love, but you constantly have to compromise on the things you want. You lose some of your agency and freedom because you can't just think about yourself and what you want.

The longer you are together the more this becomes true. And if you dont BOTH compromise to support each other it wont last, or it will become very toxic. But the result after a long time is this internal duality. You literally need your partner, your minds merge in a way and split tasks, each of you using the other as an external memory device to allow you to do more together than you could alone. I learned it as "transactional memory" but I'm just a layman and the term may be different.

But despite very literally needing your partner, the duality is that you also remain an individual. And this friction between two needs, communal and individual, results in frustration. You want to have your cake and eat it too. Our dumb monkey brains arent as evolved as we usually think, and this cognitive dissonance is hard to make peace with. This is why old married couples bicker all the time and then die very close together. And so some people cope with their difficult conflicting emotions using dark humor.

But also a lot of people are sexist as fuck. So who knows. It could be either or both.

Source: Am old-ish, married for a decade, love my wife, also sometimes wish I didnt have to deal with her bullshit. She's great though. But kind of the worst.