Somehow society perpetuates the idea that comedy in general is lowly, even contemptible. This attitude seeps out in the language; "Are you having a laugh?" is an accusation, "some joker" is a synonym for an idiot, and to be "laughable" is never flattering.
Also, the most lauded artistic achievements are generally lacking in humour, and heavy on the tragedy; films like Schindler's List will always win the Oscars, Picasso's Guernica is one of his most highly rated, and comedy is pretty much absent from a music critic's list of favourites.
So why is this?