I think that format in general lends itself to a surface-level entertainment-- even my absolute favorites like Letterman and Conan, and certainly going back to Carson and beyond, rarely got political beyond easy jabs or dug really deep. Instead, the best of them realized that, since it can never really get deep, the best thing to do is to pivot hard into deadpan absurdity. And the more surreal the show gets, the more it feels rebellious against the format.
But yeah, no network talk show is going squeeze too much juice out of the format, *especially* the monologue.