Right tool for the job.
I think if there is a sensible use-case for parallel computing in JS, it would be good to have. However, trying to make a solution before we have a (clear) problem is foolish.
I'm not saying there isn't already a use-case, but I haven't seen one that isn't already covered by languages better suited to solving those problems (e.g. Rust).
Edit to give a different example: parallel computing in JS is like trying to write a web framework in Rust. Sure, you can do it, but Node is already better suited to doing that. At best, you're making a worse version of something that already exists.
You make it sound like it was difficult to learn. Underneath, C++, Java, Pascal, C#, Javascript and Python, have many similarities and jumping from one of those languages to another in the list is very easy; compared, for example, to something like jumping from any of those languages to Forth, PROLOG, SQL, ML, Haskell, or Lisp.
Some of them are also really similar syntactically, for example this group: [C, C++, Java, C#]; or this other group: [Pascal, Algol, Go], so even the syntax doesn't get in the way when jumping from one to other.
Thus, usually, software engineers do know more than one language and they apply what better suits the program.
