I can say with certainty that it does not always work. If I plug a pair of Apple earbuds into my Android device, the audio up/down do not work. This functionality isn't consistent even within the Android device world. Having a consistent headphone jack that provides consistency here would be a pretty big win. (Even bigger if Apple gets on board, which it won't.)
> I guess I can live with it, but having to carry around an adapter from USB to 3.5mm audio will be a PITA
Pretty sure the endgame here is that your headphones have a USB C connection on them instead of a 3.5mm audio jack.
> Next year, USB power cords, and you'll have to rewire your house.
You can already buy outlets with USB ports. They're increasingly common, but thankfully the transformer is in the outlet so you're not running low-voltage wire all over.