The reasons for it in the first place. Decentralization, consensus, flagless currencies (even Steem is a currency though it serves other purposes). Proof of work and proof of stake are basic concepts if people want to know about the mining side. The rules can be set in the algorithm so users and holders of the currency know what to expect as far as things like inflation. Also the 24/7 nature of crypto currencies and not having to put your money in a bank (you can hold the private keys).