Both matureness of the ecosystem and developers are a big issue. For typical enterprise apps you just don't need the characteristics of Rust and therefore it doesn't make any sense to pay the penalty for using it. If your focus are business logic related needs (as opposed to best in class performance, no GC, etc.) using Rust is a grave mistake. Just use boring Java or better Go (better tooling, standard lib and scaling) and focus on delivering value to the customer.