It's not (only) that. C++ is driven by a commitee and those guys managed to create a (mostly) modern, pleasant programming language. Rust is driven by a commitee. It's less about commitees and more about specifically C, it attracts a certain kind of people and that certain kind of people keep C the way it is.

C won't ever get up-to-date as C proponents don't want anything modern. It's not like system languages get left in the dust though, Rust is having some exciting evolution.