Because then you lose the one real advantage of node - running the same code both server and client side. Node has to run the same javascript as browsers run in

Because then you lose the one real advantage of node - running the same code both server and client side. Node has to run the same javascript as browsers run in order to keep that advantage. That means having the same standard library. So, because it's just standard javascript, to improve node's standard library you have to go through all the w3c standards processes for a new javascript / ecmascript version with your standard library improvements, then haggle with all the browser makers to get them implemented and standardised, then wait for the users to upgrade their browsers, etc etc. It's not a simple process.