... Or, as has also been suggested, the sellers liked other teams' best prospects better.
Bloom may also be hanging on to top prospects for two obvious reasons: 1) to continue to build depth, so when the time comes that he deems the Sox all-in, he can deal for needed MLB pieces without decimating the farm; and 2) he's made some untouchable, envisioning players who may be part of the core of his someday "sustainable contenders".
Casas, for one, looks like he could be a force at first base and in the heart of the order. Duran and/or Gilberto Jimenez may also be worth keeping, until the Sox determine if either is the centerfielder of the future.