Even when they do, it is in prototype done by the paper's author, not necessarily something that you can merge right away into upstream.
Visual C++ is already there in C++20 and increasingly improving C++23 support as well.
I work on Ruby compilers and people often suggest features that they don’t realise would be catastrophic for performance if implemented, or are sometimes literally impossible to implement.
Even exported templates, as hard as they were, the EDG folks actually implemented them, only others decided not to follow upon.
The current state with clang is a mix of MIT like license, and those that profit from it not caring about upstream, even GCC is doing better.
> people often suggest features that they don’t realise would be catastrophic for performance if implemented, or are sometimes literally impossible to implement.
Oh, that's every language.