People are different.
Some people suffer immediate hearing damage when subjected to an unprotedted gunshot .. others suffer no damage at all.
I'm in the latter group. Many decades ago, when I was in the U.S.M.C. hearing/eye protection was unheard of. During two tours of duty I shot many thousands of 30-06 rounds from my M1 Garand without hearing protection.
Fifty some odd years later, my hearing is unaffected. In my 70's, my measured hearing is still as good as it was in my 20's.
During the ensuing decades I've shot hundreds of thousands of rounds and have never used hearing protection. My hearing is still unchanged.
I don't recommend shooting without protection. I demand that my children and grand-children use eye/hearing protection. I will not allow them to shoot without it. Do as I say, not as I do.
My personal life experience is that every human being is different ... unique.
Some experience hearing loss due to gunshots ... others do not.