Considering that most (Unix) OSses are written in C, it would be irrelevant for a language to scale better than C ever could.

Nonsense. A Unix-like OS is an opinionated, general purpose operating system intended to run a wide variety of applications equally well. A well-designed application tuned for a specific purpose written in an appropriate language may outperform a generic application written in C. Go look at the language used for the best FFT libraries on your system; I bet there's Fortran involved. Then look at some of the compile-time optimizations you get in languages where explicit or even implicit purity by default allows for automatic memoization and expression elimination. Throw in automatic parallelization, and you can beat C in terms of performance, scalability, and ease of development.