Vanity may be a problem with some older people, osso. That's why my mother wanted the in the ear type that were not visible. She doesn't like to wear her glasses either--she'll use them for reading, because she has to, but almost never wears them for distance because she doesn't like how she looks in glasses. Fortunately, her vision isn't all that bad, but she does see better when she wears her glasses. If she had been limited to a hearing aid that was visible, I'm not sure she would have used it. But, the in the ear type is more expensive, hers were very expensive, and not everyone can afford it.
Unfortunately, I think many older people don't have a hearing aid that works really well, or they have one that isn't properly adjusted. I've known people like that, and they just forgo wearing it. That's really a shame. I agree with you that they might like them if they worked properly. My mother loves hers--she likes being able to hear.
I also think that Medicare should provide some coverage for hearing aids because I think they are a necessity for older people with hearing loss. You can find cheap prescription eyeglasses that do the job just fine, but you can't find really cheap hearing aids, at least none that work decently. Just as people need help paying for prescription drugs, many need help paying for hearing aids, and I think Medicare should help with that.