Forgive me if I don't understand the computer science behind this, but isn't it better to have more than one of something?

For example Burger King and McDonalds.

Having more than one, means they compete and try to find ways to out perform each other.

Why not duplicate the block chain (I believe you call it a fork) into two copies that would then diverge from each other?  In the hope that they would compete and drive forward innovation.