If its what they're good at, their gonna post it. I don't think people are going to post something they aren't used to doing and it looking bad. It's like quality filtering. Subjective quality, though.
Right, but like, what's the point of mastering one thing (dragons, ponies, furries, robots, whatever the forget people like to post) and then just doing that over and over again? I like doing portraits, but I try not to repeat angles of faces, how much of the body is included, facial expressions, mediums, I try to mix it up, and I don't necessarily shy away from things that seem challenging to me. And for now, the reason I keep doing portraits is because I feel like I haven't mastered them, I have more to learn, and I'd like to get better. And once I feel like I'm at a place where I feel good about what I'm doing consistently, then I'll move on, back to landscapes, do architecture, do something else for the sake of continuing to grow as an artist.