That is because legit professional music services are not allowed to offer music from years ago, as you mentioned your service of choice does.
I talked to a DJ interested in our PrimeCuts service yesterday. He subscribes to one of these music pools. He has 5 DJs. He gets 1 subscription to the pool. He said that is all the pool makes him get. Any legit music service for professionals will tell you that you need 1 subscription for every DJ you have. We have companies who get over 100 subscriptions for all their DJs. Supposedly, those same companies could just buy 1 from these pools and be legal. I would imagine all the little guy single-op DJs wouldn't be too happy knowing a big company with a bunch of DJs pays the same amount for music as they do.
Kinda makes you wonder when the main music services for DJs (PrimeCuts, Promo Only, RPM, ERG) all have one set of rules and these pools have their own rules.