Interoperability is essential for some of the smart contracts, but it ends up undermining much of the "wealth" that's emerged because of limits. Bitcoin, Ethereum and many of the others depend upon scarcity for their value. If one can get all of the value from blockchain by using a level two or three side chain at a much lower price, well, that's going to start undermining the central chains. And if the central chains lose support and interest, well, their price will drop. That will drive away the greedy people (which may be good).