While trying to implement a make_signed_with_fallback for non integral types i noticed that std::make_[un]signed is designed to copy cv but not ref qualifiers and I'm wondering why.
The only explanation I can think of is that copying ref qualifiers is only rarely needed.
Unfortunately, there doesn't seem to be any standard machinery to copy cv or ref qualifiers from one to another type, and the only thing i could find is private in the type_traits headers (ms, clang, gcc) which makes me think that that's not very common either.
I found a old question on SO about the implementation of a copy cv ref trait though.