Designing initially for "optimum" can only be done when you can be 100% sure that you know everything. That is easy for a lamp timer. But for a large number of niches, you can't get the required customer feedback until the customers have been allowed to play with prototype units. The customers just can't visualize the product, so they can't describe what they consider important features to make your product stand out. And the developer often have completely different views of the product, so the developers can't switch hat and pretend to be a potential customer. Especially if the product is intended for users who are not too interested in technology, where there are a very big gap between developers and customers in expectations and way to use the product.