I'm not quite sure what I think about this being a regulation, but it would be easy to provide earplugs at less than $1 per pair. They are very cheap.
On the other hand, I think there needs to be more of an outreach campaign to teach people (especially teenagers) the importance of ear protection. The cheap earplugs will reduce audio quality, so a lot of people won't want to use them. You can buy yourself a set of earplugs which are designed specifically for listening to music and still being able to hear for something like $20 (probably more now because inflation). Anyone who regularly attends concerts, or who occasionally attends rock concerts, should have a pair.