The problem is that the operating system packages itself often depends on some version of a dependency. You can perfectly pip install something globally, but globally installing a library means everything else on your system is affected too.

There are solutions to this (pipenv being a popular one, though sadly often not explained to Python newcomers) and there are alternatives for that as well. You probably don't actually want to install a package like a package manager, most of the time you want to install an application and the specific requirements for that application, which is exactly what pipenv is for.

Your global package manager and your global Python package manager don't agree on what version is "the latest stable version" of a package so you just can't expect global package installs to work like that. It's like trying to make pacman, apt, and dnf work on the same file tree: you can probably get it done, but the end result will grow unstable or unusable within days.