It's not like the old headphones can't be used without a headphone jack. The 3.5mm-to-lightning or 3.5mm-to-usb-c dongles are small and relatively cheap. I just keep mine hooked up to my wired headphones.
This works great, until...
You leave the pair of headphones with the dongle behind by mistake and spend the rest of the day frustrated because you have access to a perfectly good pair of headphones but no the dongle.
Or you stick to one primary pair of headphones and are frequently taking the dongle on and off making it even easier to misplace or leave behind.
It's frustrating to have to come up with solutions, however effective, to problems that should never have existed in the first place.
I'm willing to make that trade, especially given how uncommon DVD's were even by the time the MBA launched. (Although I'll note that my desktop has a BluRay drive and I wouldn't have it any other way.)
What benefit am I getting in exchange for the loss of a headphone jack? An extra couple millimeters of screen real estate?
This is all such an unnecessary problem.