"Why don't they just..."

"Can't they just..."

"Haven't they heard of..."

or other similar phrases, please

1. Read through the linked content (or if it's a video, watch it or find a transcript), and

2. Bonus points: familiarize yourself with the problem domain.

Doing (1) will usually answer these questions all on its own. If it doesn't, doing (2) will help. In this case, we're not talking about a random amateur starting fresh on a problem nobody's considered thoroughly yet. Python's global interpreter lock is extremely well-trod ground; the people working on it are not just experienced programmers but experienced with Python; and there's a lot of background out there, available in an easy Google search, explaining what's been tried and what's been ruled out over the history of the problem.

In particular, the two problems you'd learn about from following the advice above are:

* A lot of important existing Python code consists of modules which are partially or entirely written in C and depend on the documented Python/C API remaining stable. Breaking the C API, and thus forcing all that existing code to rewrite to a new API, is considered an unacceptable solution (this rules out many "why not just use (insert your favorite GC technique here)" approaches).

* Prior attempts at removing the global interpreter lock while not breaking existing Python/C code have caused major performance degradation for single-threaded Python code, which is also considered unacceptable.