@RavingArmy I think a big reason people aren't interested other systems is the lack of experience with tabletop in general. DnD is huge, complicated, clunky, and hard to learn. It's a big investment of time to get into it, but it's heavily aided by the massive amount of memes and whatnot on social media which helps to fill in the blanks in a fully passive way.
Most people don't want to learn another system because they think it's gonna be as hard as learning DnD was (not understanding that other systems can be far easier to learn and play) and because there's no social media equivalent for other systems to learn them passively.