It's about the system behind the interface: the interplay of internal & external company processes and as well the personal & automated 'touchpoints' with the customer. It matters greatly how easy it is to place an order end-to-end, to navigate the website, to make a phone call, to handle logistics and everything else that is part of a fully integrated service model. It simply has to run smooth, easy and trouble-free while staying consistent in quality and quantity.
In an market environment where such efficiency is increasingly assumed customer or brand loyalty will ultimately decrease otherwise. Ease of use and precision come from a deep understanding of these service processes, and are all deriving from solid Service Design.