Everyone's hearing ranges differently.
Some deaf need hearing aids' just because they like a bit of noise (which to them would sound like rats or maybe bass tunes, can't say for sure).
I am not quite there, I wear one hearing aid but can't wear two because for me it's way too too much noise that shatters my nervous system and without my hearing aid I'am pretty much deaf it depends on the other persons tone or pitch friequency in their voice.
For some deaf, hearing with hearing aids causes them too much trouble because it gives them headaches and makes them disoriented and dizzy, because they can't handle the noise. For other deaf, they don't have this problem.