Earlier quoted context omitted.
>"Also if I (a programmer) want to write really really fast code I'm probably reaching for tools like tensorflow, numpy, or jax." Very limited view which ignores way too many areas.
Sure, examples?
Really, for almost any X, somebody somewhere has to do X with strict performance requirements (or at very large scale, so better perf == savings)
Most of these python libraries are only fast for relatively large and relatively standard operations in the first place. If you have a lot of small/weird computations, they come with a ton of overhead. I've personally had to write my own fast linear algebra libraries since our hot loop was a sort of modified tropical algebra once.