I think the basic argument is that USF sets take much more time and effort for potentially unfruitful results, than the other numerous projects going on here. USF sets are low on the priority list. Which sucks, I agree, because there's still plenty of great soundtracks unripped. If only it were as easy as 2SF ripping :)
No one came up with any three letter code better than 2SF. DSF would just be confusing.
USFs are, as mentioned, hard to rip. Part of that is due to the nature of N64 games, part of it is due to poor design of the format and player. And it's not as if I'm doing any other rips, and my rips tended to be lousy anyway. I'm satisfied to do a little coding and host what I can, at this point.