I would say if you look at the companies around the world, from all possible sizes, not the SV bubble, the answer is yes.

What they care is who support their tools, who they are going to call, how SLAs are enforced.

Erm... what languages are you talking about?

I mean, I've genuinely unsure.

All the stored procedure programming languages of commercial SQL servers, .NET before Microsoft opened it up, commercial compilers of Common Lisp, C++ Builder, Delphi, Ada, C and C++ compilers for embedded development (no clang and gcc aren't the only ones), Coldfusion, Flash, Objective-C (gcc and clang are just a tiny part of the whole stack), Cobol, RPG, NEWP, a few in-house proprietary languages, Java compilers for embedded platforms with extended AOT features

Let's see.

-SQL Stored Procedure Languages, .NET (used to be), Delphi, Coldfusion, Objective-C, RPG, NEWP, and AOT Java are valid examples, IMHO.

-C++ Builder kind of qualifies, as the UI language is unique. So I guess we could count most UI designers as this.

-Ada, (most) embedded C/C++ compilers, and COBOL don't count, because open-source implementations do exist.

It doesn't matter if there are open source implementations of language X, if you cannot use them in processor X, operating system Y, rather the closed source commercial compiler of the processor X, operating system Y vendor.

Quite common in embedded space.

...I said most architectures. Many do have an open source implementation of C.

Which you may not be allowed to use within the company.