I consider the concept (not the detail) of an immutable but publicly accessible ledger to be a prerequisite to comprehending why blockchains are important. Without that knowledge, you couldn't distinguish a blockchain DApp from a regular computer programme. If people can't do that, then product differentiation will never occur and blockchains won't catch on. Joe Soap must know a "little" about why his e.g. blockchain lending platform, can't cook the books and defraud him of his money.