Productivity
All people are different. In bazillion ways. Some are young, some – old. Highly educated or just in pre-school. Some like cats, others like dogs. Some have an iPhone, others use an Android phone. When we build software we most often build it for someone else to use. And the people that use that software are different from us. They know different things, they expect different things, and they like different things. So you cannot possibly expect that when you build a feature, everyone will know how or why to use it. If you bet on a wrong design people ...