I've never tried to listen to music while my iPhone is charging, never thought that was so common up until now of course.
Honestly, I personally prefer to keep my iPhone out of hands and out of use while it's charging.
Thought that was the best way to keep the wires from breaking and prevent overheating.
Edit - I cannot think of the restrictiveness knowing that the iPhone is connected to the charger on a wall/port somewhere and having earphones on, it'd require one to just sit around relentlessly and not even move the head too much.
But everyone certainly does have their own preferences so perhaps the future iPhones aren't for those? I mean if it ain't working for you, its best to switch to another no? If not then the alternatives are adapters or embracing the wireless sets and not just the AirPods but others too.
Oh hello there , the following message is sent from plain old reality. A lot of people who have jobs sitting most of the day in front of a laptop computer will have their phone charging off a USB port while listening to music off that same phone.