IMO some of the things you mention come down, really, to sunk costs. People want to play systems (and settings) they know. Learning anew isn’t inherently fun, just work. I love Hero, FATE, AD&D, Pathfinder, 5E, OWoD Mage, many others. Glad I learned FATE and 5E, but dude, I’m old, life is short. 🙂