Two reasons like I said elsewhere: (1) using multi-core architecture more efficiently and (2) eliminate state machines and use functional style instead, which is possible when you have threads (green, pseudo, OS threads, whatever) each with an execution stack. Functional code is more robust and is easier to write and maintain too.

Yeah, ok. People are not doing that.

When multicore is utilized it's normally in the line of https://unity.com/dots

DOTS is exactly what I said, as a matter of fact.