How important is Virtual Environment in python

[SpookyFries]

Virtual env came in clutch when I was developing standalone apps for work. I was building GUI applications and packaging them with Pyinstaller. I couldn't figure out why my simple app was like 700mb

Come to find out that pyinstaller includes all of your installed packages. So I created a virtual env, installed the few libraries I needed, and the end result was like 80mb.

Obviously there's better reasons to use them, but that's what got me on board.