>Inflicting -Werror on yourself is fine, but inflicting it on others is onerous, because there's no way you can guarantee that your code produces no warnings on their compiler with their library and header versions.

This is precisely the reason it is in fact necessary.

When writing code that is intended to be portable and is expected to generate reproducible floating-point calculations in numerically intensive calculations, warnings on different platforms and header versions is a godsend.

When I receive a bug report that says, "I am using operating system distribution X, version Y, with library version Z, and specific test W produces warnings when I type `make check`," it makes me happy.