Because we face global challenges.
The world of mankind, the real world as opposed to the digital world, is not divided into nation states geographically. We are simply humans spread across the globe. Our problems are human problems. We have discovered, through the expansion of the digital world, that we are basically the same. Combine this with the notion of man developing enough power that groups of men can change the way the global system of man in nature works (Capitalocene) and we end up with global challenges.
We really need a Global Council.