Why is it the all great comedians are dead?

This is not a general rule-surely, there are the Chris Rocks, Dave Chapell's, Stephen Colberts, Jon Stewarts and Bill Cosbys still left in this world. But I just discovered (courtesy of Michael) the work of Mitch Hedberg. I HAVE NOT LAUGHED SO HARD IN SUCH A LONG TIME. It takes a lot for me to forget I am sitting in not-moving-traffic on the Capital Beltway for 45 minutes (to go 5 miles). A lot. But Hedberg did it and I am sad I will never see him in concert. I feel the same way I feld after Mike introduced me to Bill Hicks many years after the fact. Damn it.