Hm, It can be a real problem if you have the joy of working with old C++ code: the initial codebase might have had its own string type, and then some more class

Hm, It can be a real problem if you have the joy of working with old C++ code: the initial codebase might have had its own string type, and then some more classes added by long-gone programmers who thought the earlier types were slow, and then newer code added by people who actually use std::string (well, you get the idea). (much to my regret, that is a true story.)