I said this before but its because when holding back a minor leaguer it is affecting a rookie. A rookie who hasn't put in his time. And players know that if the minor leaguer plays well enough to force their hand, the team will have no choice but to eventually call him up. This is putting off free agency for a 5 year vet who has put in his time. It's similar to the NFL. The players union will probably put up very little fight to a rookie salary slotting system. It will hurt players as they enter into the league, but help disperse more money to veterans. It's all about the rookie versus veteran side of the equation. And again, I ask if it wasn't considered a no-no, and didn't have negative consequences why wouldn't it happen all the time? Why wouldn't teams out of contention send down all players with options every year at this time to put off their FA by another year? The fact it doesn't happen, EVER, should provide all the answer anyone would need.