Because women don't need a sense of humor to get laid.
For a guy being funny can make up for being poor or ugly or having no prospects.
To use a card metaphor a male 3 of Clubs can become a 6 or an 8 of Clubs if he is fucking funny.
For a girl a 3 of clubs is still a 3 of clubs and a 6 of clubs is silll a 6 of clubs even if she is funny.
No one ever shared an image of a hot chick and went "Yeah but could she make me laugh tho?"
I'm generalizing obviously but there is just no demand socially for young girls to try to make other people laugh. So much less women grow up trying to do it or feel the same social pressure to excell at it.