The issue really is to do with noise dose - I.e. level and duration of exposure. The risk is based not just on level, but how long the employee works in that noisy area. Most of the time, a punter's occasional visit to a loud(ish) gig won't deliver too high a noise dose. The HSE recognises this, and says, "occasional exposure isn't as dangerous as a worker who might experience 8 hours per day, 5 days per week at this noise level, so within reason we are happy". Unfortunately, some gigs are significantly louder than others, and some punters attend concerts more frequently, or listen to iPods set to high levels when not at concerts. The provision of (free?) ear plugs was something that the RNID promoted in their "don't lose the music" campaign. This is a pragmatic approach - rather than trying to silence pubs and clubs and be branded spoilsports, they tried getting people to use some protection and reduce their overall exposure.
However, there is some risk that the sense of responsibility can be diminished if ear plugs are provided - a kind of "we've provided protection for the namby pambies, so let's turn it up and rock".
Given that many venues have still to do anything about Noise at Work 1990, let alone the version that replaced it, I would hold my breath on developments in this area
Simon