Nobody talked about "high performance". I'm just talking about using all the cores on a machine. People write stuff in Python and JS for obvious reasons that I don't need to detail here.

Performance is best judged on a logarithmic scale. Most software barely needs any, and there are many orders of magnitude between "barely uses the CPU" and "uses 100% of a core".

But once you're at 100% of a core, then there aren't many orders of magnitude between that and "uses every core". In fact, the impact from not using a scripting language is on the same order as the threading would be! So, if it's worth spending effort squeezing out those last 1-2 orders of magnitude from the CPU, then it's probably worth thinking about the language as well.

If you've already blown through 4-5 OOMs going to a full core, then chances are you'll need it.