Many reasons, here. Farm and heavy equipment, competitive shooting, blasting crews, building construction, to name a few.
Years ago, hearing protection was almost unknown, and mufflers were not all that common.
Noise induced, per my audiologist - unlike 2 of my brothers, where it's genetic.
Right handed long-gun shooters tend to have left ear problems, due to the angle of the head.
I've had severe tinnitus since age 14 - 68 now. "Hard of hearing" my azz - I'm damn neared deaf.
Don't put off getting hearing aids - the longer you wait, the more of the ear to brain connection (cognizance) you lose.
And that loss is irreversible.
