Because in JavaScript there are many different implementations of engines, and they run on all kinds of stuff. Adding something to the standard is not a small t

Because in JavaScript there are many different implementations of engines, and they run on all kinds of stuff. Adding something to the standard is not a small task, and it means that it's now extra code that needs to be installed on practically every single PC. And that doesn't remove the need for a library like this (or your own implementation) for a long time because you can't rely on a brand new release to be available for everyone.