Not because I am a diehard RL-fan, that is ranting about "how much credit rogue deserves", but simply because I am tired of boring repetative games that top the charts and lists, and is what people love to play and talk about.
I think that an average "commercial" gamer feels cheated if the game is too short, that's why commercial games are so "boring and repetitive". Also he likes to win the game, so no permadeath. Even if this is not true, that's probably what the publishers think.
I think Diablo has a slight roguelike feeling to it, even though it has no permadeath, other roguelike elements are extremely dumbed down. Although a more proper description would be, an action game with some minor roguelike elements mixed in.
I have tried playing Diablo II with another character after winning with one character, but it was extremely boring. That should not happen in roguelikes. (Original Diablo was better in that regard.)
Why has no big commercial developer, (who is aware of how superior the gaming-experience in roguelikes are, once you get into it) embraced some of the features that roguelikes represent, and used them successfully in a big title with beautiful graphics and great story elements?
I am not sure how good were they for their times, but old commercial roguelikes (Valhalla/Ragnarok, JauntTrooper) did not achieve commercial success, even though I consider them very good roguelikes even now. But of course popularity also depends on marketing, luck, and so on.