It's not so much that anybody thinks that mix is a good idea, but it's just what happens immediately in any C/C++ codebase if you're using any nontrivial combin

It's not so much that anybody thinks that mix is a good idea, but it's just what happens immediately in any C/C++ codebase if you're using any nontrivial combination of libraries at all. The feature is about providing consistency, not ignoring it.