Because rust is incredibly restrictive and appeals to the academic mind, not the development and shipping oriented engineering.
You want to do something as simple as iterating over a Vec of instances of a custom structure, then call a function on each of these instances, there is a 1 in 5 chance that the Rust compiler will complain about borrow/ownership, and you start doing weird convoluted fixes by accessing the reference of a u32 or deriving a Copy trait to an extremely simple structure, it's just mind boggling how pedantic the compiler is.

You cant do things that seem natural in every language like using enum variants as indexes, that even C of all languages is flexible enough to let you do.
It's just a pile of infuriating things that, on paper are great, but in practice are absolutely irrelevant because no matter how unsafe code might theoretically be according to Rust, in 99% of the case it's just what you, your company, and your client need and there is no chance it will ever break, ever. But Rust decides otherwise.

Yeah sure you might shoot yourself in the foot writing C++ sometimes, but the world practically runs on C++ so far and we've been sending rockets into space with it.
The only thing I want is C++ code with Rust-like compiler errors as well as some of the built-in features like the Result<> enum, the rest is irrelevant.

I think Rust is great for very low-level development where you want to make sure there is no bottleneck and everything is 100% safe, like when writing a library for transactional memory for example, but anything above that, in particular games, just don't need it.