> I am not a python programmer

I _am_ a python programmer.

> What is the use case for this?

> Who needs it?

This can be answered with a simple user story:

As "THE PYTHON STEERING COUNCIL",

I want to "GET RID OF THE GIL",

so that "PEOPLE WILL STOP WHINGING ABOUT THE GIL."

To be fair, there's another group of people who stand to benefit. Namely, any python programmers who currently believe that "threads are an easy way to make my program go faster" will soon be the recipients of a valuable learning experience.

Nice!

;)