Smart contracts are useful in the sense that they represent a decentralized system that exists between all parties to the agreement, helps to avoid conflict situations between them and saves their time without having to pay for the services of intermediaries. Blockboys have their shortcomings, but they are absolutely transparent and, undoubtedly, superior to traditional systems in speed, cost and security - that's why banks and governments express such interest towards them. I think bitcoin does not have anything to do with this!