The thing is, that the current Airpods form factor would not be socially acceptable as a hearing aid and vice versa. Right now, one of the things that Airpods do, in addition to play music is provide a visible signal to those around you that you're listening to music. Change that to maybe they're listening to music, maybe they're hard of hearing and it becomes a big social problem.
I'd add, that the fact that there's no visible indication that I'm listening to music with my hearing aids is a social negative in my relationship with my wife (although I can see it being very helpful in the future when I'm back in the office and have to be visibly present at boring meetings—I'll be able to just turn off the external sounds and settle in for an hour of podcasts or audio books or music).
