The point isn't the just the payment mechanism but the network it connects back to plus the payment mechanism.

[edit] to clarify: if vendors actually accepted (something like) bitcoin at restaurants or wherever, this would cut out the banking middle man entirely. Also we already collectively have the tech to do this now.

These vendors still need to access fiat currencies to pay wages, rents, taxes, suppliers, etc. Until workers, landlords, governments, and suppliers begin accepting BTC, there's no incentive for vendors to take on the risks of accepting BTC.