> the fact it’s likely already cached on the browser from a common CDN makes it seem quite silly to go out of your way to remove it.

This is a missconception. The problem of multiple CDN's and various patch releases of shared libaries means the hit rate is only likely to be in the 2% region.

https://www.root777.com/appdev/does-using-google-libraries-a...

Developers tend to focus on their use-case too much.