It's only about performance. asyncio is still inherently single-threaded, and hence also single core. multiprocessing is multi-core and hence better for performance, but each process is relatively heavy and there's additional overhead to shared memory. GIL multi-threading is both single-core and difficult to use correctly.

No-GIL multi-threading is multi-core, though difficult to use. I don't know the Python implementation but shared memory should be faster than using multiprocessing.

That said, when designing a system from scratch, I completely agree with you that for almost almost almost all Python use cases, threads should never be touched and asyncio/multiprocessing is the way to go instead. Most Python programs that need fast multi-threading instead should not have been written in Python. Still, we're here now and people did write CPU-intensive code in Python for one reason or another, so no-GIL is practical.

In these threads, I also always see a lot of people who simply aren't aware of asyncio/multiprocessing. I assume these are also a significant share of people asking for no-GIL, though probably not the ones pushing the change in the committee.