While I get you point, I think it's of limited usefulness for Python. You would end up with Snekr.io using 3.11 and cheeseshoppr.ws using Python 3.8.4 and etc. You can get some packages for any Python3 but they are the smaller ones. The larger wheels like numpy and pandas have C code which needs to be compiled or there's a giant version dependent wheel.

Server side Python is often deployed in a venv which has the desired python version and all the dependencies copied with the code.