Everyone knows someone with an expensive hearing aid living permanently in a nightstand drawer. The usual explanation is "they just didn't work." After a decade in the business, I can tell you that's rarely the whole story.
More often one of a few things went wrong — and almost none of them are really about the device:
Expectations. Hearing aids don't restore hearing the way glasses restore vision. The brain has to relearn sounds it tuned out years ago, and that takes weeks, not minutes.
Fitting and programming. A device that isn't dialed in to your specific loss will sound harsh, tinny, or useless. That's a setup problem, not a hardware problem.
Quitting during the adjustment period. The first week is the hardest. A lot of people give up right before their brain would have caught up.
The real tragedy is that plenty of "bad" hearing aids were fine devices that never got a fair shot.
The Hearing Aid Handbook spends real time on this — the unglamorous stuff that decides whether you become a happy user or another drawer story. Because the most expensive hearing aid is the one you don't wear.