A key reason for this, if I may guess is that most libraries today provide tutorial/get-started code which uses CDN. I assume most just copy paste these code snippets into their projects.
My go to test for my QA team is to have them add a zero internet test case. Test your product in localhost with the network switched off.
My go to test for my QA team is to have them add a zero internet test case. Test your product in localhost with the network switched off.