I don't know what to say other than I am pretty sure I have never encountered it before. I have been coding for over 30 years, 20 years professionally, and have never seen it. You can see by my account age and comment history that I have been active on HN for 15 years.
I actually have interest in game programming, too. So I don't know.
I am sure I'll encounter it 10 times this week now, good old Baeder-Meinhoff
Though to be fair it kind of makes sense that you would have never used SDL yourself. It you never go that far down the stack and do stuff like write your own game engine and the like, you wouldn't really need to know it. I guess I am more aware of software dependencies as a Linux user? That is my only explanation or maybe you are really just one of those lucky 10000.
I actually have interest in game programming, too. So I don't know.
I am sure I'll encounter it 10 times this week now, good old Baeder-Meinhoff