the security of a blockchain in directly tied to the number of users actively participating. You need to incentivize users to keep participating indefinitely. You do this by rewarding them with something that they value. As the number of users dwindles, so does the network's security. So how can a blockchain work on anything that isn't a cryptocurrency? If it's not a currency, then it can't be used to motivate people to participate in the network. After all, you are spending real money to pay for the electricity to mine. If there's nothing to pay you back with, that's just money out of your own pocket. Who the hell would accept such a deal?