I used to run tournaments and ran well over 300-400 bar table tournaments. My only pay was that the owner would pay for my entry into the tournament. And a beer if I wanted it, which I usually did.
I can count the number of times I was tipped on 1 finger.
But I wasn't in it for the money, I was in it for the tournaments and I enjoyed it. I was never expecting tips but appreciated the one I got. That was also a long time ago and I don't think anyone ever thought to tip the TD.
Now I'm in a completely different place financially and so now I tip generously. One small tournament I always do well in the TD is the bartender and plays in it. I usually tip her roughly half of whatever I win. Up to about $30. So if I get $20 for 3rd she gets $10. If I get 80 for first she gets 30. (I take out my entry if I win.) Once she had a second TD so I tipped them each 20 when I won.
I actually play better if I feel like I'm playing for someone else who needs money so I use that as motivation.
I don't think everyone should tip that way or that it should be the standard. I don't donate to charity so I try to make up for it by tipping generously to people who facilitate doing what I like to do. So waiters, golf caddies, pool TDs, etc all get a little extra from me.