Design applies equally to what the product looks like for its users (the outside), how it is constructed internally (the inside), and the efficiency of the path that it takes from its conception to the supermarket shelf (the business). 

Each of these points are just as important as the others. No matter how beautifully elegant your product is, it would be worthless if it does not do its job to the expected standard. No matter how efficiently it solves the problem at hand, it won’t last long if it is more expensive to manufacture than the users are ready to pay for it. No matter how cost-effective the process and genius the inner workings are, no one will use the product if it is sophisticated and ugly.

You got the idea. You need all three.