These aren't simple pad left functions. Good luck making a Core-JS on your own. All of these are crucial to basically everything continuing to work - and more importantly massive security risks if their maintainers stop.
what do you mean by "making on your own"? The first example(time zone db) is portrayed as "holding up" 4B android/iPhone devices, and Google/Apple for sure have the capacity to create something "on their own".
Did you go and read the tzdb? Go ahead, it’s on github. There is so much amazing historical info in there, clearly many years of research went into making it.
Apple/Google can create something that works somehow, but they can’t replace the knowledge that went into making tzdb. And whatever they make won’t be universally accepted.
These aren't simple pad left functions. Good luck making a Core-JS on your own. All of these are crucial to basically everything continuing to work - and more importantly massive security risks if their maintainers stop.