I don't play usta leagues, but in the GCITA (greater cinci indoor...), it's about allotted time. If you can squeeze three sets into the time period, you play them out. If you are out of time and on serve, you play a tiebreak for that set, whether it's the first, second or third. It's all 9-pt tiebreaks, first to 5.
When indoors you have to set some kind of time limit, in the end it sucks, but none of us are getting paid for this, so it is what it is. I've won and lost many matches by one point. In the end it has made me a stronger player mentally in those clutch situations.
The catch is, if you are up a break in a set, say 3-1, and time is up, you win that set... so sometimes you get losers who start to prolong time between points when they are up a break and time is running out, so you don't get a chance to break back. I'd rather play a super tb instead of lose a set 0-2 (which has happened too often as well).