Before the iPhone, traditional cell phones already had smaller headphone jacks: a 2.5mm one was pretty standard. One of the innovative things the iPhone did was replace the smaller port with a standard 3.5mm jack, which allowed people to use regular (potentially high-quality) 3.5mm headphones with it, rather than a crappy 2.5mm headset. The decision eliminated pointless proprietary-ness to integrate with a more vibrant ecosystem.
Job's decision on the iMac to embrace USB and drop the Mac's proprietary ports could be seen in a similar light.
I wish those kinds of decisions were the ones present-day Apple decided to cargo-cult.
Whenever a USB port is involved, it's usually smashed and requires soldering to fix. Given that most modern phones have AMOLED screens, and those cost 200$+ just for our store to buy the part, and that many phones require you to remove the screen to get to the charging port.... Well you see where this is going.
The explanation that made sense to me mentioned 2 design constraints:
1) the jack surface-mounted to the PCB took up space that conflicted with an edge-to-edge LCD/OLED display. If you've ever disassembled an iPhone, you'll see that removing the home button and extending the backlight assembly to the bottom edge means the headphone jack has to go away.
2) waterproof phone. The traditional jack was always an entry point for water damage.
Apparently, Apple studied millions of phone users and determined that more people wanted waterproof phones with bigger edge-to-edge screens than the headphone jack.
Samsung has no problem making waterproof phones with headphone jacks. I'm not sure why, if you can put a USB/Thunderbolt/whatever jack on a phone and still be waterproof a headphone jack is some an intractable problem.
The explanation (possibly inaccurate) I read was that the waterproof jacks were more expensive. I noticed the new Samsung A8s has copied Apple's decision to remove headphone jack. Sony also removed the headphone jack. There seems to be an unavoidable engineering+cost motivation that causes multiple companies to remove that jack. Is it the edge-to-hedge screen? extra space for the haptic feedback? Better battery life because it doesn't feed the analog circuitry for that 3.5mm jack? I don't know.
Sure, and there are perennial rumors that real soon now that will be reflected on flagships (first the S10, but then that faded, now the rumor is either the Note 10 or S11.)
> There seems to be an unavoidable engineering+cost motivation that multiple companies (including Sony) to remove that jack.
Well, yeah, of course, if nothing else, it takes space that could be used for something else. The Samsung Note 10 rumor centers around trading it for a bigger battery, for instance. Obviously, it's not a trade-off free choice, and what it's traded for may not be the same between different manufacturers that decide to axe it. (The same with SD card slots, which lots of manufacturers have done—even Samsung several flagship generations back, though they reversed.)
I personally think that more headphones should have the threaded 3.5mm jack on which you can adapt either the 1/4" jack or say, a usb-c or lightning adapter. This would effectively make it a permanent addition to your headphones without having to keep track of a separate dongle.
I was looking for one because one of our cars has no bluetooth, and the other has bluetooth that won't talk to any recent iPhone, and my iphone 5S is getting flaky. Wish I hadn't missed the SE over the weekend.