Gaming was what held me back from switching for decades. Steam is doing a great job on that front, most recent (like in max 5 years old) games in my library work like a charm under Ubuntu. And that includes all AAA games. Old games are harder as those are, understandably, not on top of the priority list to convert to Linux. For those, and some rarely used other stuff I haven't bothered to figure out Linux alternatives for, I still use Windows.

If Linux based gaming continues on the current trajectory, I could imagine a world in which a great chunk of the consumer market switches from Windows to Linux.