It's the same reason why containers are used as a solution to a problem created by bad practices. I miss the times where Python projects/libraries were like, yeah if you have something between 3.6 and 3.9, you are good.
If your software needs Docker to be easily installable, you've done something horribly wrong. If your Python projects needs a venv with versions pinned to the patch level, you've done something horribly wrong.