The internet as most people know it and as companies depend on it isn't that old.
The difference being discussed here is a single existence vs. potential for redundancy. The best way for something to outlive even the places it's stored is by repetition. That goes against both how we've grown things so far on the internet as well as the talk about competition among instances and the biggest one wins. It's far better for there to be many groups that share information in some way but are their own entities and aren't dependent on the rest.