It's a self-fulfilling prophecy, too. Or maybe a self-perpetuating machine. The OGL really does play a factor - if you could slap 5e compatible on a Kickstarter it'd do numbers that blew anything else away. I remember Jeremy from Three Black Halflngs addressing a listener complaint about how their show had a D&D focus and they ran D&D actual plays primarily and he flat out said on the air: look, we've run other systems. We do episodes featuring other systems. We have the listener numbers. We have the subscriber numbers. You want to do a podcast about your favorite system? I support you, I wish you luck, go for it, but we are trying to survive and make a living out here and the fraction of listeners we get is too small when we change systems. Hell, Critical Role has the biggest viewership in the industry and I watch those numbers - 3k for their own system (Daggerheart or Candela Obscura, the latter of which is DELIGHTFUL) and the got 100k last week when they switched back to D&D. But that's the arts in general. Gotta feed the beast that feeds you back, be it pop music, D&D, or scraping the serial numbers off a major comic book IP and hoping nobody notices.
Two of the people I DMed an actual play for a few years ago left and switched systems and they got single-digit views/listens for a five month run. I mean it was humiliating to watch. But I admire their attempt.
Anyway, all this and I'm thinking I will have gone my ENTIRE life without being a PC in a long-term game from beginning to end, but I will have DMed something like 8-10 multi-year campaigns to completion since 2019, and it feels like both an accomplishment and like I've missed out.