Sadly, "being fashionable in UNIX circles" is more important than it sounds, because those circles have quite a lot of skilled people, mindshare and staying pow

Sadly, "being fashionable in UNIX circles" is more important than it sounds, because those circles have quite a lot of skilled people, mindshare and staying power and they contribute to lots of critical components that only now are (partially) considering to accept contributions in a different language than C, and that's because that language is Rust (see Linux, GNOME, etc). The refusal of C++ from those "UNIX circles" has led to decades of reinventing the wheel from people that reimplemented all sorts of weird hacks in C for reasons that basically boil down to a strong, unsatiable desire to avoid C++ at all cost (see Glib, Gtk+, etc).