This question strikes me as somewhat obtuse, but I will attempt an answer:

NVIDIA and AMD.

These are only two GPU manufacturers of any significance. (Intel is also a player, but not a major one.)

They supply SDKs (drivers and libraries required for software development) for their products that support C and C++ and precious little else.

There have been attempts to reverse engineer the toolchains in Rust but as I understand it they are not yet mature.