Except the ones who want to do things that are 'forbidden' by RMS. Those people have no choice but to use LLVM. For example, a lot of academic work on compilers and languages can't easily use GCC, neither can people wanting to make more sophisticated tooling.

The point of GCC is having a good compiler available to everyone, for any use. Not to be embedded everywhere in the look-but-don't-touch fashion.

See also Linux kernels in most Android phones. That's exactly what GCC authors do not want.

I think it has to do with their plugins API, or lack thereof.

Clang currently supports my freedoms more than GCC with its political limitations holding it back.