This thread is, as ever, degenerating into personal taste.

No, Health and Safety. It is a fact of law in the UK, all employees have to be offered and made to wear ear protection, if the ambient levels are deemed sufficiently high. And that includes volunteer stewards. But no provision in that law to enforce it for audience. Because they have a choice. Companies comply IME for fear of litigation.

But not so Folk Festivals (I don't go to other types).

FWIW there have been cases of concert musicians suing orchestras because of hearing loss. Trumpets are not only loud, but full of high frequency energy, and it is the shortest cilia that snap off first. Age and diseases like the common cold affect them too. Which is why teenagers can hear up to 20Khz and older people barely register those sort of frequencies.