What if we had something similar to the #numpy API on the #web and in #node etc? V8 is faster than CPython sure but you still can't get close to the performance of a hand-crafted SIMD number crunching loop written in C when writing #JavaScript (or using #WebAssembly for that matter). You kinda can in #Python thanks to numpy.
You may argue that most web/JS things don't need that level of performance.. but for sites which want to do e.g some pretty complex image prcoessing, SIMD would be great