My main reason: Because I'd like to use headphones that are compatible not only with my phone, but also my laptop, iPad and various other devices I regularly use them with, and are easily replaceable everywhere in the world if I should lose them.
You have no idea what you are talking about. There are plenty of professional headphones and other studio equipment that use the 3.5mm plug. In contrast, no one uses Bluetooth headphones in the studio for any serious work.
you travel for 15 hours continuously? Probably not for you. but for those that have a regular commute the ear buds will work for 3 hours. but the case contains a battery too, and will recharge the buds 2 to 3 times, so as long as you're not listening to them for more than 3 hours continuously, then they'll charge while you're not using them and actually give you 6 to 9 hours of play time before you need to plug in the usb cable to charge them up again.
I know exactly what I'm talking about, and no one anywhere in the world is previewing, monitoring, or listening to 24 bit lossless audio through a 3.5mm jack. Guess again.
Yes. I fly from the US west coast to Europe several times a year. Typically takes 15-18 hours including one stopover. These tiny Bluetooth earbuds wouldn't even last from San Francisco to Chicago. Heck, I sometimes use my earbuds more than 3 hours continuously during a normal day at the office (conference calls and music). Headphones that last just a few hours are not really an option.
The digital to analog chip and the amplifier chip are mediocre in the phone. High end headphones don't get enough power from the built in components. With digital output via lightening port the headphones can supply a much more powerful DAC and Amp. Inline or at the headphone itself. There are some headphones that do so now, high end headphones that sound much better.
They are pretty good for a phone in my experience. But yes, they are obviously limited by the phone's power supply.
Only if the headphones have their own batteries that can provide more power than the phone's. Otherwise you have exactly the same restrictions whether the DAC/amp is in the phone or in the cable.
And they work just fine today, without abandoning the 3.5mm jack that the majority of people are using.
If you travel regularly most likely you can expense two sets one can be in use the other recharging in pocket. That gives you 18 hours of use.
Measurement based reviews of the iPhone DAC since at least the 5 have shown it to be an excellent performer, often beating external "audiophile" options. It's flat and clean; there are no perceptible deficiencies in its ability to reproduce audio. The amplifier is not sufficient for high impedance headphones (a constraint of size and battery), but high impedance is not automatically better. If you really want high impedance headphones with an integrated amp, then you can already buy them, as you just pointed out.
