One important point I haven't seen mentioned yet is that SDL is the defacto minimal compatibility layer on Linux for writing a windowed 'game-y' application if you don't want to directly wrestle with X11, Wayland, GTK or KDE.
Yeah - getting an OpenGL (and presumably same for Vulkan) context is surprisingly annoying if you don't have a library to help you. It also works quite differently on X11, Wayland, or directly on kernel APIs. Many games that don't otherwise use SDL2 (such as ones ported from other platforms, i.e. most games) use it just for that.
