https://www.buzzfeed.com/johnpaczko...adphone-jack?utm_term=.fwjmoX1o5L#.hunDmvomEZ
A lot more in the piece pimping those airpods and more.
TLDR: Headphone jack was removed for new camera stuff, haptic feedback home button, remaining space was filled with a bit more battery. Don't expect any flagship iphone to have a headphone jack ever again. Oh god please buy Airpods.
For Dan Riccio, Apple’s senior vice president of hardware engineering, the iPhone’s 3.5-millimeter audio jack has felt something like the last months of an ill-fated if amicable relationship: familiar and comfortable, but ultimately an impediment to a better life ahead. “We’ve got this 50-year-old connector — just a hole filled with air — and it’s just sitting there taking up space, really valuable space,” he says.
...
“It was holding us back from a number of things we wanted to put into the iPhone,” Riccio says. “It was fighting for space with camera technologies and processors and battery life. And frankly, when there’s a better, modern solution available, it’s crazy to keep it around.”
A tentpole feature of the new iPhones are improved camera systems that are larger than the cameras in the devices that preceded them. The iPhone 7 now has the optical image stabilization feature previously reserved for its larger Plus siblings. And the iPhone 7 Plus has two complete camera systems side by side — one with a fixed wide-angle lens, the other with a 2x zoom telephoto lens. At the top of both devices is something called the “driver ledge” — a small printed circuit board that drives the iPhone’s display and its backlight. Historically, Apple placed it there to accommodate improvements in battery capacity, where it was out of the way. But according to Riccio, the driver ledge interfered with the iPhone 7 line’s new larger camera systems, so Apple moved the ledge lower in both devices. But there, it interfered with other components, particularly the audio jack.
So the company’s engineers tried removing the jack.
In doing so, they discovered a few things. First, it was easier to install the “Taptic Engine” that drives the iPhone 7’s new pressure-sensitive home button, which, like the trackpads on Apple’s latest MacBook, uses vibrating haptic sensations to simulate the feeling of a click — without actually clicking. (Did we mention that Apple killed the physical home button too?) Taptic Engine vibrations will also be used to deliver feeling specific notifications — hitting the end of a scrolled page, for example. And because Apple has given developers an API for it, an awful lot of other stuff as well — particularly in games.
...
Second, there was an unforeseen opportunity to increase battery life. So the battery in the iPhone 7 is 14% bigger than the one in its predecessor, and in the iPhone 7 Plus, it’s 5% bigger. In terms of real-world performance gains, that’s about an additional two hours and one hour, respectively. Not bad.
Even better, removing the audio jack also eliminated a key point of ingress that Riccio says helped the new iPhone finally meet the IP7 water resistance spec Apple has been after for years (resistant when immersed under 1 meter of water for 30 minutes).
...
Schiller thinks it’s a silly argument. “The idea that there’s some ulterior motive behind this move, or that it will usher in some new form of content management, it simply isn’t true,” he says. “We are removing the audio jack because we have developed a better way to deliver audio. It has nothing to do with content management or DRM — that’s pure, paranoid conspiracy theory.”
...
“Remember, we’ve been through this many times before,” says Schiller. “We got rid of parallel ports, the serial bus, floppy drives, physical keyboards on phones — do you miss the physical keyboards on your phone? … At some point — some point soon, I think — we’re all going to look back at the furor over the headphone jack and wonder what the big deal was.”
A lot more in the piece pimping those airpods and more.
TLDR: Headphone jack was removed for new camera stuff, haptic feedback home button, remaining space was filled with a bit more battery. Don't expect any flagship iphone to have a headphone jack ever again. Oh god please buy Airpods.