Blender ships with its own version of Python, so for normal users it does not matter what the system’s Python is. If you do development work, it is easy (and even recommended) practice to make use of virtual environments / Anaconda environments.
What would be a reason to not upgrade to have access to new features? As a add-on developer, I’m happy there is support for Postponed Evaluation of Annotations among others. And upgrading between minor versions in Python 3.x is usually problem free.