Rather than a lengthy diatribe into the presumptuousness of starting a question with "Is there a reason", I will give you the literal answer: As far as I recall, no one tried.
"Rather than a lengthy diatribe" You are too kind.
"Is there a reason this hasn't been ripped yet?" There is, and it's the same reason the other remaining 90% of N64 games haven't been ripped either. Simply, the few people who were active in USF ripping weren't interested enough to do it at the time.
Anticipating a follow-up question: no-one is active in USF ripping currently, so it likely to remain unripped. unknownfile is AWOL, ugetab passed away, and everyone else has moved on to other things. I'd recommend looking for a soundtrack, line recording or do some of your own recordings from an emulator if you just want the music to listen to.
The whole point in the rip is to get every song in the game. I'm hardly going to get every song in the game if I've never played the game before and don't know what songs are in the game.
What do I want the rip for? Custom streams (BRSTMs). Simple. Infact, both soneek and I wanted this.
"The whole point in the rip is to get every song in the game. I'm hardly going to get every song in the game if I've never played the game before and don't know what songs are in the game."
Makes no difference. If you can't either find the music online in some format or record it yourself you're shit outta luck.