I don't think it's unreasonable to say that people connect to more than a single pair of headphones with their phone. That puts you back into dongle carrying territory.

Sometimes I walk to work without bringing headphones, then use the pair I leave at the office.

I have an Aux cable on the stereo in my living room that my friends occasionally use. Should they make sure to always bring headphones to the bar? They're not planning to listen to music at the bar, but at least they can convince themselves they didn't lug a fucking dongle around all evening just to play music pregaming at my place.