Garbage collection is very hard to combine with real time, and at the kernel level it is unacceptable (because it introduces a pathway with very hard to bound latency).

Since that is the exact use case that interests me when it comes to languages such as C, Rust and D I would rather see the whole thing taken care of at compile time with very strict rules about how long it can take to traverse a certain piece of code, especially when it runs on the other side of the syscall interface.