I don't think any of us are sure Radar... about what causes it. I know that I read somewhere back in the early days, of a man who had screaming tinnitus and had managed to get rid of it completely by using a special back rest in his car. He was convinced that it was a posture problem. I bought a back brace thing in the first few months and wore it at my desk - it was supposed to ensure correct posture. I wasn't convinced that it helped though and stoppped wearing it after a while.
It could also be that the way we use our brains makes us more susceptible to tinnitus. Or that there are more of us on here from IT because we use computers more than others.
So many possible causes - you can go insane wondering & reading & investigating.. and mostly not really getting anywhere.
I'm just happy that I am coping with my T (most of the time.. I still have bad days!) without drugs, without becoming depressed (yet!) and that I still really believe it will go away completely eventually.
More conjecture but my posture is not wonderful either, along with a pinched nerve in my shoulder which comes and goes. (yes I'm a wreck!)
As you rightly say though, you can go nuts trying to second-guess the cause. Keep calm and carry on seems appropriate.