There are some obscure features in OpenGL like line stipple or selection mode. Most of them have been deprecated for over a decade, but there is still some CAD

There are some obscure features in OpenGL like line stipple or selection mode. Most of them have been deprecated for over a decade, but there is still some CAD applications that rely on these functionalities and ancient OpenGL 1.3 semantics. It makes no sense to use silicon space to implement such features, if you can emulate them in software. Also, doing things in software doesn't always imply slow, because many old OpenGL features can be reimplemented with modern OpenGL using shaders, so it's done by hardware, just there is no dedicated HW support for it.