Because you might still want to use them. That’s been the case for many many releases.
If you DO want to delete them, use Windows Programs and Features to uninstall them.
A lot of people have had this problem, which if I understand it right (I use a Mac, so don’t have first hand experience) is a combination of recent Windows 10 updates causing graphics problems for many users (not just for SU), and problems with out of date graphics card drivers providing less than full support for OpenGL 3.0 or better, which SU 2017 now REQUIRES. You can no longer uncheck ‘use hardware acceleration’ as you could in older versions, to get the CPU to do the graphics processing.
Make sure you have the latest drivers for your graphics card (from the manufacturer, or if a laptop, the laptop manufacturer), and see if rolling back some recent Windows Updates will fix the problem. There’s a variety of causes, and some fixes work for some people but not others.
See this thread: