Dick Cavett thought of himself as a serious journalist, and he conducted himself as such. Letterman was foremost an entertainer (as was Carson). But he also (

Dick Cavett thought of himself as a serious journalist, and he conducted himself as such. Letterman was foremost an entertainer (as was Carson). But he also (credibly) acted the part of cultural critic. Letterman laid some of the groundwork that John Stewart ultimately perfected. And, as a sibling comment notes, Letterman had widespread (mainstream) reach. Much more so than any of the other fine examples that you cited. It is only appropriate to close this comment by quoting Letterman himself - "if you accept the premise, you'll enjoy the show."