Not it didn't. The work on Qt standard on 1991, according to Wikipedia. The work on STL only started in 1994 and became a standard with C++98, and even then it

Not it didn't. The work on Qt standard on 1991, according to Wikipedia. The work on STL only started in 1994 and became a standard with C++98, and even then it took time for compilers to get decent standard support. So every library needed its own string implementation. New libraries generally use C++ string, unless they're have very strong opinions about performance that trump interoperability (e.g. Facebook's folly). But seriously, isn't that hypocrite to blame old C++ libraries for implementing their own string class, and then go espousing C? C of all languages - the language whose spartan standard library includes almost nothing (including usable string processing code, if you care even slightly about securing your code from memory errors), and each respectable C project ends up implementing their own lists, queues, maps, stacks and of course strings.