It's not easy being funny.
People expect things of you. They come to you down in the mouth, looking for a laugh. Most of the time you can oblige them, but it's hard creating something from nothing. I'm not a music box that you can wind up and expect to hear a tune. At least say "please."
I guess it comes from watching too much television. Sitcoms really mold a kid who spends half his day on the couch. That, and a willingness to tell the truth to people's faces.
Anyway, it's easy to ask for a laugh. It's just hard to deliver sometimes.