The auto-failure is actually much more troubling than auto-success, because it denies participation. If Expertise is in play, I have to worry about maybe setting DCs up to 30 because the Expertise guy might hit them. But what about the PCs with no chance of hitting that DC? Should I tell them not to bother rolling? (That always feels like inappropriate metagame info to me.) Auto-success as a special ability is fine because the game is chock full of auto-success already and players kind of expect that from special abilities. If Expertise isn't in play, I literally don't even consider DCs above 20, I just tell the players that approach won't work.
To be honest, the chance of success is boring to me and I don't want to spend any brainpower on it. I think RPG rules fixate on pass/fail odds-of-success mechanics because such rules are super easy to design, learn, and execute. I'd much rather spend time thinking about the consequences of success and failure. One of those outcomes is usually more interesting than the other, and often Expertise automatically picks the boring one.