I think the framebuffer devices is a least common denominator that is available on even miniscule or emulated hardware whilst anything above thats starts requiring a whole lot more infrastructure.

And honestly, you don't need much more for an image viewer.

I shudder when I read DRM after building a embedded display raspberry pi build. There was a problem with Raspberry pi kernel incorrectly detected an HDMI display was connected even though I was trying to display to DSI. The only work around I had was to write a kernel module that would disable HDMI as a possible interface.