Ergonomics of a software application (also: user-friendliness, usability) is crucial for the user acceptance. Whether an app catches on in the market can largely depend on ergonomics, on the design of UI (User Interface) and UX (User Experience). That's why companies such as Amazon are constantly improving their UI/UX, Amazon has dozens (even: hundreds) of deploys every day (sic!) to improve the ergonomics of its application. The One-Click-Buy is a well-known example for a major improvement in ergonomics.
Google's developers go even one step further: They have se the goal of creating a standard for the design language. If the icons for printing, switching off, play, pause and so on are identical in all applications, this will make it easier for users to find their way around applications. This is the goal of Google's Material Icons.
