DAVID LETTERMAN

David Letterman on CBS

David Letterman on CBS

The flap over ABC's failed bid to lure late-night comic David Letterman from CBS — thereby ousting Ted Koppel's venerated “Nightline” news show — basically came down to this: Koppel just can't sell beer like Letterman. Behind the scenes of this star tussle lie the hard realities of television advertising. Koppel's “Nightline” may get higher ratings than Letterman's “Late Show,” but Letterman attracts significantly more younger viewers. And that's appealing to beer companies, movie studios and car manufacturers that covet young audiences and are willing to pay top dollar to the television networks that ...