I don't deny there are benefits of bluetooth, but there are benefits from a 3.5mm jack too.
A £50 mixer takes these inputs (almost all from 3.5mm sources) and brings them all together via a reliable tactile interface.
On the road of course I only tend to have to choose between 2 sources, so perhaps beats can approach the utility of a 3.5mm audio cable.
If a phone would have to cater to all these edge cases we'd still have serial ports on them.
As I say, I can live with a dongle for 3.5mm or serial (despite it being a regression), it's just another straw.
The certainty and simplicity of an audio jack is not valueless though, no matter how many people on HN say it is.
Nobody is saying that audio jacks are valueless in general, just that it's reasonable for a mass market device where it has value for a small % of people to not have it.
With some Bluetooth headphones you could just listen to both devices at the same time without plugging / switching anything. It also has upsides.