Actually, looking at this I'm surprised that the mainstream browsers are still caching javascript, but not some pre-parsed/compiled version of the code.
Obviously browser support is one fairly big component. (I've long wondered how much of Chrome's ~65% is straight-from-dl.google.com evergreen, but I guess that's just commentary).
Then there's tooling... heh. That'll be its own eternal September just like JS has been I guess.
> Chrome 42 introduces an advanced technique of storing a local copy of the compiled code, so that when the user returns to the page the downloading, parsing, and compiling steps can all be skipped.
Not sure what's going on in Google Cloud UI, though. It's a dumpster fire.