What?

You can't run Node on embedded systems, because there isn't enough memory.

A compiled zig program can be only several kilobytes with no depedenencies.

Array access programmed in low-level languages can be optimized with SIMD and parallelization, which will be orders of magnitude faster than the same thing on Javascript. Text processing, image manipulation, video processing, hashing, etc.

There is like infinite reasons to not use Javascript.