A rolling stone gathers no moss.1
When software in a particular category stops rapidly evolving and its interface begins to develop along a set of accepted patterns, designers begin to decorate. Decoration is a luxury, it is something you can only afford to do once the functionality of the thing you are working on has been implemented to a high degree. It is in the period of gradual evolution and established interaction norms that designers begin to decorate, begin to focus on small aesthetic details for the visual experience alone. Prolonged times of slow evolution lead to decorative excess. Unable to differentiate software on the level of how it works, developers try to push it ahead on the level of how it looks. When the buttons in all the apps are the same, when the controls all appear in about the same place, when all the interfaces are laid out in a similar fashion, designers begin to differentiate their work by changing the appearance of the interface rather than its function or its structure. The interface begins to gather decorative moss.
The recent minimalist trends in software design — Metro, flat, iOS7, Material — are attempts to scrape away the moss without a radical alteration in the underlying function. It is a reaction to the friction felt between the old stratum of software that has cemented its implementation and thus could afford to wear a rich visual coat, and a new stratum of software that yearns for a radically different approach to interface design. The old and the new cannot co-exist in harmony because the appearance of the two look nothing alike. The layers of visual excess painted over old software apps — e.g. skeuomorphic visuals, rich textures, reflection effects, etc — became baggage to designers who wished to develop something new, for example, using animation to help differentiate between the different states of the app and create a more fluid experience. If you wish to move content around, scale things, change colors, morph one element from one into another, all the superfluous visuals like gloss and textures simply get in the way. Minimalist design makes animation simpler.
The old paint was scraped away not for the sake of a minimalist style, but to allow the designer to create a new kind of experience, an experience where the content making up the interface would be more alive and more dynamic than ever. Buttons morph into panes, panels bounce back and forth to reflect the speed of the finger used to pull them across the glass screen, bits of content fly from place to place signifying a change in state or context, icons move or change shape, and everything gently slides in or fade out as you navigate around the digital canvas. Without the baggage of skeuomorphic visuals, rich textures or decorative styles, the designer can now experiment with motion, can begin to craft a new kind of visual experience from the content itself.
The saying has two interpretations. In one, moss is seen as a sign of stagnation. If you don’t act, if you don’t keep moving, you will begin to rust away. In another, moss is seen as something desirable. If you keep changing projects, if you keep losing focus, you will never be able to build up anything worthwhile. I think the duality of the message is quite fitting for the analogy in the post. Excessive decoration is bad design, it is a distraction that adds unnecessary baggage to our work, but decoration is also beautiful, something that enhances the experience of people using our work. Decoration is not in itself good or bad, just as design is neither good or bad — it is how it is implemented that makes all the difference.