As I understand it one of the main reasons Porsche have done this is to assist in resale for the Porsche dealer network. More and more add ins like sat nav and a hands free phone kit are becoming required accessories in vehicles at these levels, and with the current set up even if the original owner never wanted the sat nav it can be added at a later stage to make the car potentially more saleable on the used market - hence all the buttons will be there whether you use them or not.