Even in these domains people still balance performance against the expressiveness of the language, or else why wouldn't everyone write their games/HFT/robotics in assembly for that "bare metal" performance?

For example, many popular game engines provide C# scripting engines _even though_ using a garbage collected language (even just for scripting) is slow (and throwing away % of performance) because the performance is _good enough_ for their usecases.

That's because scripts in a game are not usually a performance bottleneck if kept to best practices. And you can bet your ass both unity and unreal have some ASM in their guts.

Yes, my point exactly, and in the places where people use OCaml, the overhead from not monomorphising generics isn't a performance bottleneck.

That's a self fulfilling prophecy. Of course OCaml isn't used there... Because it can't hit the performance target.

Exactly, I mainly work on a C++ software and for my PhD rewrote all the core algorithms in OCaml... Boy that was slow, I'm never ever touching that language again for anything that needs peak performance.

Yeah, that's why I asked, who cares? If you care about it, then obviously you need it. Also, https://news.ycombinator.com/item?id=28283376

Well, Jane Street do HFT in OCaml.