They probably haven’t yet because of backwards compatibility. I’m certain there’s plenty of companies that take advantage of the quirks unique to MSVC++ and would be quite upset if it was just replaced with GCC or LLVM.

This, exactly. MSVC is full of extensions so heinous and horrible to make you scream when you sleep at night. They probably pledged to support those until the end of time, so I guess they would have to keep CL around forever.

Also, if you manage to overcome how horrible their CLI tools are, Microsoft's CL is a nice C++ compiler. Their STL support is great nowadays and lots of things just work; I even had seen times where they were _stricter_ about standards than Clang/GCC, which honestly shocked me.