Parroting what others said above about secure boot and arms race and all of that, consoles have solved this problem by controlling their environment, cryptographically signing everything with unknown keys, and preventing custom software for the vast majority of users. If secure boot can't solve it, an arms race becomes tiresome, and a PC is too general purpose to be locked down to the degree necessary to mimic the solution consoles have, I wonder if a custom OS mode would ever be considered. Windows Store kind of solves these sort of problems, but everyone hates it. What if Microsoft came out with a Store mode that you could boot into, where everything non-store was impossible to execute, and game developers miraculously used it and gamers miraculously accepted it.
Just thinking...
