Your right about the many causes. No real cures yet either.
I have had high frequency tinnitus for 30 years in both ears. As I age and my hearing gets worse, so does the tinnitus.
Inner ear hearing aids helped cover it up 15 years ago pretty well. Not anymore. I have progressed to BTE aids 2 years ago since they can be made more powerful, and I put them in as soon as I get up, since my ears are really screeching at wake up. The aids still help but don't cover up the high pitch constant noise between my ears, and they help me hear my wife, particularly if looking at her and some TV, news type. Stuff with music backgrounds and people talking low is just annoying.
So in my case, my brain can not hide the constant ringing any more even with multi-programmed hearing aids.
At least I'm not totally deaf yet, and appreciate the hearing I have left, even with the tinnitus..
Wearing hearing protection on the tractor, chain sawing, or working in the shop is a good idea, and I wish I had done it
much sooner. Now with the ringing, and no hearing aids, wearing hearing protection really make the tinnitus squeal worse.