Reading up on it more, from the OpenGL website, if OpenGL is not properly installed:
"Without drivers, you will default to a software version of OpenGL 1.1 (on Win98, ME, and 2000), a Direct3D wrapper that supports OpenGL 1.1 (WinXP), or a Direct3D wrapper that supports OpenGL 1.1 (Windows Vista and Windows 7). None of these options are particularly fast, so installing drivers is always a good idea."
So even if swiftshader is avoided, it doesn't necessarily help much. It's a shame we can't just install OpenGL with the application.