I don't think any of the third-party JS is for functionality. Many large companies call out to 3rd parties not because they don't want to write code, but becaus

I don't think any of the third-party JS is for functionality. Many large companies call out to 3rd parties not because they don't want to write code, but because they're using marketing services so they can do things like re-target users for ad displays on other websites. (also many top N companies do use 3rd party code, like React, but they usually re-host that themselves)