If you're delegating decisions to intelligent actors, why not delegate to intelligent actors who make a payment app that's denominated in dollars and includes none of the complexity of Ethereum?
Because for some reason I enjoy using a smart contract blockchain as the platform for my interactions. That might be for example because I also want the ability to use the service with a multi-signature wallet... or because I have been locked out of PayPal for political reasons or because I am a vendor of erotic literature (https://www.engadget.com/2015/12/02/paypal-square-and-big-ba...)... or because I want the ability to pay in a number of cryptographic tokens... and so on.
Ethereum has value even if it doesn't involve somehow replacing all real world services with cryptographically proven algorithms. Interfacing smart contracts with external actors is a really interesting frontier; see for example Vinay Gupta's latest venture, Mattereum. http://internetofagreements.com
