You're getting lots of explanations for why people don't switch to rust, mostly existing projects, but I'd like to point out that plenty of people still start new projects in C++ as well. Most game dev has to be c/c++ if you want to release on consoles. This isn't technically true, but in practice it is most of the time. Not everybody wants to program in rust's pseudo-functional style. Some people like C because if you can generally map nice C code to its assembly in your head.

In my opinion, memory safety also gets a little overblown. Most applications don't really need memory safety, and for the ones that do, C++ smart pointers are good enough. I'm sure plenty of people will have strong opinions against that.

Ultimately there is this sort of energy towards c++ because there are orders of magnitude more projects and developers that use C++, and it would be silly to stop work on C++ every time a C++ killer came along.