I think many people would consider 60fps to be a minimum and 30fps to be almost disorienting, even for casual games.

Gamers often go for 120-240Hz monitors even.

Especially retro console games, where sprites might flicker at 60Hz (either to create an illusion of translucency or because of hardware limits on simultaneous sprites displayed); viewing footage at 30fps can end up catching all the "off" frames and make screen elements disappear completely.

I don't watch too many of those, and those few that I do are more 4X (Civ, Stellaris, etc), so that maybe that's why I don't notice it as an advantage for most of the content I see.

Playing at low framrates is a lot worse than just watching though.