This is at least partially because there is a performance overhead to calling out to C from Java or Go so eventually the optimal implementation of something will be in the language itself. Rust's zero-cost calls to/from C is a positive in that it gives you a large ecosystem of existing code to use but a negative in that people are more likely to just try to build "safe" wrappers around those instead of writing something safe in Rust. This is somewhat countered by the "rewrite it in Rust" folks but you still get more C wrappers than Java or Go.