This is actually not true, or well, maybe it is true, but late night comedians really didn't become that political until Stewart (and even the show he took over was very much apolitical before he took it in that direction). Carson, Leno and Letterman were all pretty apolitical. Letterman was probably the most political of the three, and even then it was sparse. The turn to late night being super political is pretty recent within the last decade, hosts before then tried to be as broad as possible, and Fallon is obviously trying to say within that old mold, but it's just not what people want anymore especially when you have people are so talented on commentary on politics like Colbert and Meyer.