They do seem to have just merged in support for Web Workers though, which I've been following for a while: https://github.com/nodejs/node/issues/43583
So I don't think they're opposed to standardising, but it's trickier when you have some past cruft built up. Lets not forget that the fetch() standard was built for browsers, and is a bit of a stretch to make it work on servers at all. You have to diverge from the fetch spec to even make it make sense in a server environment (with things like Cookies handling off the top of my head).