They all have roots going back to a time when C/C++ were the "it languages" for UI and systems development. Java was nowhere near ready for that sort of thing;

They all have roots going back to a time when C/C++ were the "it languages" for UI and systems development. Java was nowhere near ready for that sort of thing; Mozilla tried anyway, but Rhino is the only thing from that project that really took off. No other language even came close: Tcl/Tk had the UI part, but its performance wasn't up to par, and most other languages either didn't have the performance, or didn't have the UI capabilities, or called out to Tk to get the UI capabilities and thus inherited Tk's problems. Mozilla tried the low-level guts/high-level UI approach anyway, using JavaScript because they had to implement an engine for it anyway. But it took them a few tries to really get it right, and its false starts in this category remain infamous to this day. The others stuck with C/C++ for everything because it's what worked at the time, and continue because it works for them. Mozilla's at it again with Rust, though, and that looks like it could be an interesting project.