Kevin Kennedy, former Red Sox manager and Rays analyst, gave an interesting reason for banning beer etc. on the last leg or a road trip. It is a liability issue. Even the Rays under Maddon ban alcohol on the last leg of road trips. There have been numerous incidents of players having accidents and DUIs. So this is why it is done. BV had the same policy when he was with the Mets reportedly according to Kennedy after an incident.
Given the money at stake with these payrolls, this kind of move appears fiscally prudent if nothing else.