Because the concept is pretty poor, really. A bunch of comedians madly "riffing" on things no one, least of all them, really care about. Black's show is crap too. This was a 1 star video, until the last minute.
Of course it's rubbish. But the rubbish now is not as enjoyable as the rubbish when I was a kid. You younger people missed out on the age of truly golden rubbish.