Could you elaborate on why? I worked at a co that almost exclusively ran Alpine containers with a single Python app. No use of virtualenv. Never experienced any hangups with this.
But tlrd is: if you "apt install some-utility", then "pip install something else", you may have upgraded packages that some-utility relies on but is not compatible with the new version anymore.
I'm not saying never install globally, just let's keep in mind that this can lead to real issues which may be very surprising / hard to debug once in production. Unless you understand exactly what and how is delivered with every change, defaulting to venv is a safer option.
If you can prove it doesn't apply, then sure, why not install globally.
In one sentence: "Installing the latest aws-cli on an image is preventing new AMIs based on that image from booting due to the above issue with urllib3."
While this specific issue wouldn't affect docker images since you normally don't run cloud-init on them, it's just luck that it wasn't some other utility affected instead. Next time it can affect docker images too.