(FILES) US television host Stephen Colbert arrives for the PaleyFest LA screening of "The Late Show with Stephen Colbert" at the Dolby theatre in Hollywood, California, on April 21, 2024. 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. (Photo by Michael Tran / AFP) (Photo by MICHAEL TRAN/AFP via Getty Images)