Cutting out 12db makes a huge difference (as decibels are measured on a non-linear scale). It can make the difference between hearing this for the rest of your life or not: https://www.youtube.com/watch?v=0HIfqyHbKgY

In my case, in college, I would go to a club or show that was hearing-damaging probably at least once a week. Hundreds of shows a year, so I think that would qualify as very frequently as you say.

One of my friends was in a band and over the years that I knew him, I noticed he started to mix down his own music recordings hotter and hotter on the treble. I asked him why he was doing that and he said "I don't know, this is just how it sounds good to me." Later I realized that he probably has hearing damage and doesn't realize how much treble is in the mix for normal ears.

Keep in mind that 85db for sustained periods of time is the low end where noise induced hearing loss can begin. That's not really that loud. It's likely that your headphones can crank out over 100db and many people work in environments with loud, constant ambient noise.

Ah yes, from one a week to hundreds per year is definitely going to have an important effect

Bands usually should be using ear protection as well.