It was never only about benefit to consumer.
Look back to all Apple design criteria for iPhone, and they religionlisly follow it until they can't any more, 1st thing Apple change on every new physical design of iphone is thinner. What it means is they are going to find a way to be thinner, if possible, and it is possible by remove 3.5mm port. Then follow by create more marketing oppotunity for Apple. Lightning cable was one, now it is BT headset. Next is cost saving. Remove 3.5mm jack will be part of it.
Every company tell consumer they are there for them. What they mean is they are there for most of them, not all of them. If Apple continue make case thicker or even remain same, they will lose a large portion of customer who has very little technology knowledge expect case to be thinner, because thinner has become an expectation to new iPhone design.