Not everything that is important can be quantified and measured. But not everything can be identified based on the human instinct side either. A balance must be struck for the clearest vision and best guidance.
One of my favorite aspects of my job is discovering new workflows and new ways of using software in order to accomplish the same task. Systems should be designed to be flexible (to a point) to accommodate some of these different desire paths; it boosts customer satisfaction and loyalty.
Flexibility allows users to use the system in the way that makes the most sense for them, allowing them to quickly finish their tasks and move on to the next thing on their plate. This makes happy users, and happy users are some of the best advocates you can have.