I agree that there's certainly usefulness for bitfields in the industry, but I haven't seen a good proposal that addresses the main issues that C bitfields have. And in rust, any given proposal wouldn't be super useful if it always required unsafe.
The Rust standard library should concern itself with very general patterns that could feasibly enable interoperability across crates. I'd rather see a generalized facility for working seamlessly with composable 'optics' on Rust structs/objects (similar to the existing support for Iterators) than something strictly focused on the bitfield case.
