Comment by johannes1234321

That was circumvented once by CDNs hosting common libraries so that those would stay in browser cache, browser vendors then "broke" that by caching per origin. (So that an evil site can't detect whether a user had been on some target site before by testing whether assets are fetched from cache)

Issue probably is that the standards process is slow (unless it is a feature Google "needs") and full of bike shedding (which features and how exactly they'd look) and adaption of features by developers is slow.

JavaScript meanwhile should be stable enough as an environment to allow a broader standard library.

Luckily it is slowly getting better (see Temporal as new date library, replacing moment.js usage in many places)