Drifting off – US late night talk shows no longer must-see TV [Video]

America’s late night talk shows once were appointment viewing, but with ratings tanking and ad revenues plummeting, their coveted place on the small screen is in question.

The hosts of yesterday and today — comedians from Johnny Carson and Jay Leno to Jimmy Fallon and Jon Stewart — are household names, and their jokes were once mandatory conversation starters at the water cooler.

But NBC, home to “The Tonight Show,” hosted by Fallon, recently moved from five new episodes a week to four — a sign of the not-so-great times.

“Late night TV is just not that relevant in today’s television world,” said Jeffrey McCall, a professor specializing in media at DePauw University in Indiana.

Each show follows a similar formula — a host sits behind a desk and celebrity guests tell funny anecdotes, promote their latest work, and even play …