You are quite right when you say that there is no need to explain cryptocurrency to new people, just prove their usefulness. By showing the result we arouse the curiosity of those who do not yet know about STEEM blockchain, they will always end up finding the answer if they investigate well.

edit: "We've built a park with a cryptocurrency called STEEM" is much more powerful than saying "STEEM is a blockchain and a cryptocurrency that blah blah blah blah..."