I blame the floppy disk. For years, it served as the icon for "save," clearly illustrating to the user that your data would be written to that flat square thing with the hole in it - a digital representation of hardware, guiding you to your intended goal. Clicking that icon would block the UI with an hourglass cursor, and reward you with the familiar grinding song of a floppy drive.
And then in 1998, Apple introduced the iMac- with no floppy drive. Though some computer makers continued shipping floppy drives for more than a decade, most of the industry quickly followed in Apple's footsteps, abandoning those square disks. But bizarrely, the icon persisted.
The modern term for using digital graphical representations of real-world, physical items is skeuomorphism, and recently, skeumorphism's been taking a lot of heat. Apple's Calendar app, with its rich leather and beautiful stitching, might be heavy-handed, but it also looks a lot like an old-timey paper desk calendar. And there's the rub.
There are two reasons to take a physical approach to digital design. The first is obvious: to make things pretty and stylish and to allow the designer to show off their incredible Photoshop skills. It's this aspect of skeumorphism that seems to rile some folks up. The second, more altruistic motivation behind the design philosophy is to create something that the user is immediately familiar with. That familiarity is comforting, and can help humanize an otherwise confusing, cold piece of technology--something Apple has always been good at.
Before the iPhone, smartphones were bulky, simplistic, and overwhelmingly digital. Apple's approach to the problem was to first connect with the human holding the device, then present you with neat things you could do with it. Advertisements for the iPhone and iPad never discuss features; they show human beings using the devices to enrich their lives.
In the more than five years since Steve Jobs gave us our first look at the iPhone, many third-party developers have opted for designs that mimic Apple's approach. Apple smartly built its developer tools to favor standard UI elements, giving the company an early edge in the then-burgeoning app wars by raising the bar for the average app's visual design. The highlight lines, shadows, and gradients of iOS weren't just pretty, they made the iPhone's software feel like a real thing for the user to touch. And for a device driven exclusively by touch, this was a very important relationship to establish.
When people started downloading apps from the App Store, they found interfaces that seemed familiar. As long as everything looked and worked like an iPhone app, there was nothing new to learn. When Apple moved toward the physical look, much of the third-party developer community followed suit.
Internally, even Apple has copied Apple; much of the style and flair of iOS's skeuomorphism has made its way to Mac OS X, presumably because of the mainstream popularity of the iPhone and iPad. Familiarity is comfort is trust. Give the people what they're used to.
It's curious how Apple's hardware and software have taken such divergent paths. Looking at iOS hardware and software separately, one might think they were produced by different companies. The drop-shadows and textures of iOS stand in sharp contrast to the clean lines and invisible seams of Apple's hardware. Comparing major models of either the iPhone or iPad line, Jony Ive's industrial design team seems to be on the march, creating devices that feel ever more like they're carved from a single block of magical stone. So why is it that Apple would ship these devices with software featuring deep shadows and visible stitching?
A lot of people see this reliance on physical representation as condescending, which has led to a skeuomorph backlash and an emerging trend toward flat, minimalist design. Letterpress, the delightful Game Center-crippling word game, consists of solidly-colored geometric shapes, and relies heavily on sound and typography to guide the user through the experience. The to-do app Clear has eschewed buttons entirely, opting for pure gesture-based control.
With the benefit of hindsight, Apple's visual design choices seem to stand alone from even their interaction design. One telling example is Apple's own version of the save icon: there isn't one. On iOS, saving happens automatically with no intervention from the user.
This may seem like a small convenience, but the move away from the long-standard file system is actually an even more profoundly important move away from thinking of your content as data. Instead, it's just stuff--ethereal yet tangible all at once. You care about your own access to it and whether or not others have access. The rest is confusing semantics.
Hardware and software alike are trending toward conceptual simplicity. It's just taking a little longer for software to look the part.
Steve Jobs very purposefully built Apple to be a skate-to-where-the-puck-is-going company, and while skeuomorphic design has acted as a bridge between the physical world and digital abstractions, it's becoming increasingly obvious that the world is comfortable with digital now. Technology is no longer witchcraft to be feared by the masses. We've grown accustomed to having phones, tablets, and computers around us to do things. With both visual and interaction design, we're nearly past the point of real-world metaphors being useful, and the simplest representation is usually best.
Jony Ive is famously minimalist. Putting him in charge of all things design should be seen as recognition by Apple that the world is ready for software and hardware to work in concert, not just mimic one another.