With the new iPhone models firmly out the door and racking up impressive sales, it has become obvious that Apple isn't in any rush to manufacture handsets that sport a bigger screen.
To be fair, a change in screen size would have been unlikely for this year's iPhone; to date, we've seen the product undergo a radical refresh roughly every other year, so it's really no surprise that the iPhone 5c and 5s are incremental--if excellent--updates to the iPhone 5's original design.
Still, big phones are everywhere these days--so much so that the press has felt it necessary to attach the horrible portmanteau phablet to those models so large as to tread into tablet territory. Thus, it's only natural to wonder whether Apple, which has so far steadfastly refused to budge on the form factor, will follow suit.
When bigger is better
Of course, there was a time, not so long ago, when the iPhone was the big phone. When it first launched in June 2007, it entered a market where manufacturers had spent decades miniaturizing the large, unwieldy handsets of the 1970s and 1980s. The focus was on smaller, not bigger--and even the smartphones of the time were large only because they had to fit both a keyboard and a small screen.
With the iPhone, Apple's great insight was to get rid of physical keyboards altogether. Given the industry fixation on smaller phones, the folks from Cupertino could have also decided to stick with something more like their competitors' tiny screens, ending up with a small form factor (think a square iPhone). Instead, Apple went with a full-size display, and the rest, well, is history.
And then there was the transition from the iPhone 4s to the iPhone 5, in which the company designed a bigger screen to accommodate a new, widescreen format. Remarkably, it managed to design a new handset that was bigger, but still managed to feel smaller than its predecessor: To this day, whenever I pick up my old iPhone 4 to test an app I'm working on, it feels massive in my hand, even though my eyes tell me that the newer model has a larger footprint.
The complex puzzle of design
All of this is to say that Apple isn't afraid to change its products' form factor; as with almost everything else that the company does, however, it's very careful about what changes it makes. Instead of "the biggest phone," the company wants to make "the ideal phone."
The most obvious advantage of a bigger screen is that you have more pixels to work with. That means being able to display more of a webpage or text document, and, ideally, taking full advantage of high-resolution video to produce crisper, more detailed images.
While on the surface this is a good thing, screen size is only one of many different design decisions that make a good smartphone. The iPhone may not be the biggest handset on the market, but that's because Apple has focused on making sure it feels good: It fits into hands large and small; it can easily be used with one hand; it looks natural when you're holding it to your ear; and it slides in and out of any pocket without effort. For contrast, on a recent trip to Best Buy, a friend took a picture of yours truly holding Samsung's Galaxy Note, which bore a certain resemblance to a scene from the classic Top Secret!
The developer factor
It's true that some websites don't render well on the iPhone's screen. However, the reason is not the small screen size but, rather, the fact that the site's code is not optimized for smartphones. When developers know what they're doing, mobile webpages are often easier to use on the go than their desktop-bound counterparts, with important information readily available when you need it in a hurry.
Speaking of developers, different screen sizes and resolutions would be unlikely to meet with approval from the people whose apps populate the iOS ecosystem. One of the many joys of writing software for Apple's mobile operating system is that there are only three resolutions to work with; this makes pixel-perfect designs easier to achieve and allows great apps to be built in record time.
A larger phone that sports a higher resolution would throw a monkey wrench into this process; unlike the transition from 3.5-inch to 4-inch handsets, which was made easier by the fact that the width of the screen remained the same, an all-around bigger screen would mean either coming up with completely different designs or giving up on pixel perfection altogether--neither of which sounds like the kind of scenario that Apple would want to foist upon its developer community.
Asking the right question
Ultimately, it seems to me that screen size is a bit of a red herring. It's an easy differentiator for manufacturers--certainly easier than coming up with actual innovations--and one that analysts can latch onto when they try to explain away Apple's continued success in the face of relentless competition and falling prices.
The real trick is coming up with the right screen size, and that's something that Apple has, so far, managed to do very well. I have no idea whether the company plans to change the size of its screens, and I'm sure that, somewhere in Jony Ive's labs, prototypes of all shapes and dimensions are being manufactured and tested continuously. If a bigger iPhone is going to eventually hit the market, however, I hope that the question Apple chooses to answer is not whether it needed more pixels, but why.