can't there be decentralized off chain smart contract? can't you have smart contracts in anyway with raiblocks?

after all a cryptocurrency is nothing but a distributed ledger of numbers, what the competition should be about is which ledger is the most efficient and secure. i consider a smart contract an add on/feature, something that is designed to make cryptocurrencies more usable, but isn't it better for mainstream adoption and the future of a currency that these things don't go hand in hand?