It's not, it's just confirmation bias after hearing it's really common but it's just an exaggaration.
Like If I were to say "What's up with all the Latino Fire Using characters?"
You've got Fire, Magma, Hotspot, That Inhuman guy, Firebird, Spectacular Spider-man made Molten Man a Latino, Robbie Reyes, El Diablo.
But that's from my Ass.
It's just that phenomenon where if you're told about a pattern or new thing you're more likely to notice it, even if it's not really more prevalent.