Qt has been around for a very long time. Work on it started in 1991. Back in the early 1990s, standardization of compilers was basically non-existent. There was Microsoft C, Turbo C, Watcom C, AT&T's C implementation for their flavor Unix, BSD's implementation for their flavor Unix, GNU C, C for the Mac, and so on. Each had some basic core functionality, and each saw the need to extend the core to handle basic things such as strings instead of just a group of characters. But, they all did it a little differently.
Because of this, many people working on Unix machines resorted to GNU C. Since GNU C was freely available as a source, it could be installed (with a bit of tinkering) on almost any machine. When I encountered a new system, the first thing I did was download, configure (by hand), and build GNU C...