I have done zero R & D on over the counter aids. I think they will have some merit if they just increase the volume equally across the frequency spectrum. If they are adjustable to accommodate particular frequency deficits they could be a real tool. Not that I'm an audiologist but it would be interesting to manipulate my own prescription.
If over the counter aids increase the number of people entering the hearing correction world, they have their place. I would have tried an over the counter pair of aids years before I actually got aids with a prescription. It wasn't a matter of being labeled an old deaf guy, it was a fear of spending lots of money that didn't really help that kept me from being a consumer. For one reason or another, consumers shy away from hearing aids. I once saw a stat on the number of people in need compared to the small number of consumers. No different than glasses.. if they increase your quality of life... why be without?