tinnitus is caused by people listening to music that is too loud. Music is too loud at most venues, if you are standing where you are meant to.
EDIT:
people don't like this comment, and point out that in many places inserts are available. All the same, the general clubs that I go to where I live, don't have them, and, more to the point, nobody else wears them. it's a social problem and perhaps a marketing problem. many bars / clubs are too loud and I as a consumer haven't been solicited to pay for a solution on-site. (even if this exists.) others I'm with don't wear anything either.
The responses here have convinced me that I likely should invest in some and bring them with me - but I don't like that I'm the only one doing so, and it seems kind of anal. i'm just being honest about how I feel. it would be easier if they were more readily available / being sold, and if everyone were using them.
I like to be cool and do the same thing everyone else does. just being honest.