An interesting observation that I find has less top do with "hearing protection" than with music being considered a distraction to some.
As it relates to recordings, both in new music and embedded audio in video, the overall volume has increased. The "loudness war" is alive and well in audio recording/production.
As far as live music, I agree that the volume has gone down but I believe there's a few other reasons for that. We need obviously to consider the genre of music. Not too many "rockin' guitar bands" are in vogue anymore and most music made nowadays is made with samples, etc. It's almost like the expectation for live music is that it should sound like a home stereo turned up slightly.
But...I think the biggest reason for the overall decrease in volume is quite simply that loud live music interferes with peoples ability to have conversations while attending shows. Sad to say, but I have been to so many shows in the past years where the audience doesn't really listen or show any modicum of respect for the performer. They freely talk over performances or walk right up in front of performers and take selfies by the stage.
Sorry to be such a downer, but I think we've entered the age where the people who enjoy music the most are the ones making it. The general public's attention is drawn to the ever present smartphone.