How many times will it take you forgetting your dongle to just pony up and buy the apple approved headphones? How long will it take you using the non-default, non-apple, non-sleek, clunky dongle as you show off your fancy new iPhone 7 to your friends before you decide it's got to go? What if they're using it the apple-intended way?
How long will it take before nobody buys headphones anymore? A few generations until they deprecate the dongle since nobody is using it? Where you can no longer buy a $10 set of headphones at a drugstore and plug them in? Where 'every audio device must provide analog audio output in a universal format that every device has been able to read since audio was invented or it is functionally useless' is no longer a maxim?
Long-term, we are giving up a universal and open protocol that all devices work with for a proprietary one. If you don't expect companies to abuse this to make money and to stop you from doing what you want with your equipment, well, I've got a bridge to sell you.