I don't get it. SDL has an event/messaging queue, cross-platform hardware support, basic collision detection, it packs its own stdlib, a cross-platform file storage API, a camera API, a pen API, asynchronous I/O, metadata/property support using its own hashmap, a geometry API that lets you throw triangles at the GPU, and other things, but all 99% of people ever seem do with it is open a window and an OpenGL context.

I've seen plenty of projects where people use it and reimplement things it already does because they want to minimize dependency. The entire point of using a library like SDL is dependency! Use all the things!