I think there is a large portion using decent headphones (the one Apple supply have always been crap) that they can use with their phone or computer that use standard 3.5mm jacks. I am not trading my Bose sound-cancelling headphones or various in-ear headphones for the rubbish white plastic Apple-supplied ones.I don't care about the adapter. It will have lighting headphones in the box. Also both my 2010 and 2015 cars have both USB audio. The 2015 has bluetooth audio.
I think there's a small portion who need to use legacy headphones or older audio equipment with the iPhone using a 3.5mm cable. And the adapter will do for them.
Looks like I either buy another iPhone 6s to keep me going, or switch to Samsung - even the Samsung Gear 2 looks better than the Apple watch.
Apple seem to have peaked and are not listening to their customers - even in their computer section. No Mac Pro upgrades, software that is being dumbed down, a MacBook that has the worst keyboard I ever tried, although that is probably to make you buy an iPad Pro where the keyboard is actually better than the MacBook.