I'm relatively lucky, my hearing is still better than most, but it does suck.
I've decided I will never go to another club, and in bars I wear ear plugs. I have more to lose, since any additional damage will likely make my tinnitus more severe.
Seriously though, hearing is one of those things you don't think about until it's too late. Protect your ears.
Your mind is very quick to normalize the volume level anyway, no matter if you're with or without protection. Why suffer permanent damage then?
That said, clubs/shows play music way too loud, and I occasionally hear the beginning of tinnitus, so I 100% agree that people should get a pair.
Also I've noticed that I can hear the music much better with them in (when it's too loud I have a hard time distinguishing pitches—singers often sound like the Chipmunks) and some groups don't fare well when you turn down the volume a bit (they use volume to mask lack of ability).
But I've been using them too late because recently I have tinnitus in the evening before I go to sleep (I do wear the plug at night as well). Am in mid 30s.
I can also leave shows, take them out, and hear normally immediately after. No more laying in bed that night being annoyed by minor hearing damage.
You don't even have to be self conscious about it, they're barely visible when they're in.
Most venues I don't find it to be an issue, but one I was at recently was absurdly loud. I was sat at a 90 degree to the stage, and in one ear I could hear the sound crashing off the back wall to the point vocals were difficult to make out because it just sounded so muffled. Blocking that one ear instantly made it a much better experience.
On the plus side, I find it way easier to understand people talking to me in the club when I have them in.
If the sound engineer isn't wearing ear plugs, the same logic probably applies. Noise-induced hearing loss has roughly the same effects on your hearing as earplugs, acting like a shallow lowpass filter.
* Sound engineer is wearing ear protection -> sound is tuned according to that bias (unless they are completely auditory neutral) -> you get the best sound by also wearing hearing protection
* Sound engineer is not wearing ear protection -> sound engineer probably has hearing damage due to prolonged exposure (and has a similar effect as hearing protection) -> sound is tuned according to that bias -> you do NOT have hearing damage, so you get the best sound by wearing hearing protection
The effect on the sound is the same in both cases and the correction is the same in both -- wear hearing protection. It only becomes the same sound regardless of what _you_ do in the long term, if you also get hearing loss due to prolonged exposure.
What they feel are inaudible sound waves at a frequency that makes some tissue/bones(?) resonate. But this is as much "feeling" the music as is being punched in the face in sync with the base rhythm ;)
Fortunately I don't have a significant tinnitus, but was it certainly was a wake-up-call and I protect my ears much better now.