The thing is: If you use a non-C/C++ language you'll inevitably have to interface with some C or C++ code (your OS API, whether that be POSIXish or whatever.).

The thing is: If you use a non-C/C++ language you'll inevitably have to interface with some C or C++ code (your OS API, whether that be POSIXish or whatever.). There can be a lot of friction/impedance mismatch at this point, especially if your language uses novel ways of managing resources and/or memory. I'm guessing this is why a lot of Application-level GUI code still gets written in C/C++, e.g. in Qt, KDE or GNOME. "Worse is Better" is Worse in the long run, I guess.