I was wondering is there any 'rule' that determines which tournaments have a tie-break in the last set and which ones haven't. I don't know if it's just a thing of the tournament or what. I have always found it 'funny' that in some GS the last set is a tie-break and in other ones it isn't that way. So I'm curious about that. Why is that?. Why aren't all the tournaments in the same way?