Who did they have to convince?  Do the players care much about international amateur bonuses?

The union cares about anything that gives them leverage.  They might not care about how much a 16 yr old Dominican signs for but they care about how they can use this to get something else.  The top related thing on their agenda is to completely get rid of the penalties for signing FA's. 

There was quite a bit of opposition to an international draft at the last CBA.  This was a way of forcing it.  Couldn't get it right there, but certainly could ensure it at a later time by implementing one of the more bassackwards systems out there.