The reason is to let the kids learn on the job so that they are ready to play once the time has come.
If it were truly what you think, Jose Abreu and Avi Garcia wouldn't be here. Neither would Miguel Gonzalez, Wellington Castillo, or Joakim Soria. That is $40 million right there that if what you thought was true, wouldn't be here. Turning this around, why would the Sox be spending money on these guys if the object was truly profit?