It’s something called instant gratification. Generally speaking, audiences would rather hear a rapid-fire series of one-liners. Also, it seems there has grown a sort of snobbbery concerning slapstick. I think cartoons have something to do with that. Most of the Loony-Tunes classics, as well as other animations of that era (1930–1940) which contained a lot of slapstick, were not necessarily created for children. They came to be known as children’s fare in the ‘50’s and ‘60’s, when they were used on children’s programs. When children of that generation grew up and outgrew the children’s programming, they also tended to completely discard the animation genre as well as the slapstick.