C lacks sympathy with nearly all additions to hardware capabilities since the late 80s. And it's only with the addition of atomics that it earns the qualification of "nearly". The only thing that makes it appear as lower level than other languages is the lack of high-level abstraction capabilities, not any special affinity for the hardware.

For one, would expect that a low level language wouldn't be so completely worthless at bit twiddling. Another thing, if C is so low level, why can't I define a new calling convention optimized for my use case? Why doesn't C have a rich library for working with SIMD types that has been ubiquitous in processors for 25 years?