Why do dad jokes exist but mom jokes dont?

They do. What about "Yo mama" jokes.

Mums are scary

I make my kids laugh all the time, and they like to be around me, but they associate me more with physical and mental care and support than they do with the laughter.

The joke's on us. We're stuck with the dads.

How often do you hear a mom tell a bad joke? Not very often. It's just more of a thing dads try to do.

Look up George Carlin bit about "yo momma" jokes and the Dozens game

"Being the mom friend" is a typical mom joke.

Mum jokes do exist..
Like yo mama is so dumb…

They do exist