Unless a product, service, or system is usable, people will get frustrated and will abandon it. Usability is a factor for screen-based outcomes like smartphone apps. If too many options are hidden behind “hamburger” menus or fancy icons, an app can be hard to use and just frustrate users. The same goes for physical interactions. Phablets are hard to hold onto. Ordering custom burritos at a restaurant that requires patrons to visit five different condiment kiosks can be annoying. Ease of use… or at least, intuitive usability facilitates experiences that feel in line with the design outcome’s primary function.
Some design outcomes are more usable than others just because of the way they are designed. Think about websites: when booking a flight, a person using the site has to select and input a lot of information. Destination, dates, times, prices, seat options, personal information… a lot of steps go into booking a flight. Booking a flight can go wrong in many ways.
Nielsen’s Heuristics: 10 Rules to Better Usability demonstrates concerns designers face when designing usable outcomes.
Notice how these rules were all geared toward helping users as they use the design? Each heuristic endeavors to help empower users instead of becoming frustrating. The more usable the product, service, or system, the less likely people are to bail on it out of frustration. Usability has a significant impact on people’s experience with a design outcome.