Things we see may make us laugh; things we hear may make us laugh, too. Our sense of touch may make us laugh, if someone tickles us. Why then, do our other two senses lack for humor? Where are the humorous tastes to make us say, "that's the most hilarious flavor!" What about comical odors?
If there were humorous smells, there could be scratch-n-sniff joke books and comic perfumes. If there were humorous tastes, comic chefs could prepare laughter-inducing sauces. (And psychics could have a humorous sixth sense. "I just had a laugh-out-loud premonition!") We would be better off, I think.
Update: I explained this idea to some friends over dinner, and my friend Tracy said that she had encountered a humorous taste, when she was served a salmon-flavored milkshake.