Copycats and government intervention in other words.
OK, let's say you forked the bitcoin chain right now. Would you expect robm-coin to be more succesful than the main chain? If so, why? If not, why would other copycats be better off?
If you don't agree on a currency you can't trade, it's as easy as that. Which means that it pays off to use a chain/cryptocurrency that other people use as well.
Who's to say. It would be organic. It will be fascinating to see how it works out. Unfettered libertarian capitalism, for now at least.