50 years ago in USAF basic training with the M1 Carbine I do not recall using hearing protection. Did anyone in the WWII, Korea, or early Vietnam (pre 1965) era recall using hearing protection during basic training ?
WWII kicked off a campaign of hearing protection because so many vets had hearing damage. It was not until 1983 that OSHA mandates started to appear. It was not until about twenty years ago that the Army started pushing it. These days it is well stressed in good units.