I think it's that Myst was released in a hungry, undersaturated market, and the competition is a lot tougher now. I truly love what Cyanworlds is doing, but the fact of the matter is, I'd rather be playing TF2 Classic, or Animal Well, or Captain Toad: Treasure Tracker, than Obduction.

Another problem is, their games were popular at a time when most people didn't even have an internet connection, and therefore had far more patience for offline gaming. Their games require a LOT of patience.