Once I paid a tattoo to a friend through the steem wallet and everything was even simpler than doing it with my national currency; in that moment i understood in my own experience the adventages of the cryptocurrencies in general

Now, what you propose is also interesting: pay for a service through upvotes and in the end it is money paid !! so why not?

obviously the vast majority of people do not have enough steem power to do this type of shopping, so I think this would also be a very good motivation for MANY people to start investing more in STEEM