Do you mean games like Prey and Black Ops 2? Or less action-oriented games like Chrono Trigger?
I guess it’s great for people that like it, but a different ending by itself isn’t enough of a replay value. I’ve replayed some single-ending games almost a dozen times simply because they’re fun. Not because it’s a different outcome every time.
That’s not to say the games I mentioned are bad, quite the contrary. They’re great games.