Ahh, you mean like that. Well, that of course works, but then people are not using steem as a currency, but only as an investment and then they exchange it for fiat currency or something else to buy stuff.
And it's not only how to use steem to buy, but how to sell stuff for it. Having a third party to go through is usually very inconvenient.
We can have a real economy when steem can be used as a real P2P currency, without any middlemen.