Today the NHLPA rejected the proposed plan to re-align the divisions into conferences, in a move that makes little sense in terms of the argument presented by the union. The official reasoning is "players questions about travel and concerns about the playoff format have not been sufficiently addressed"; which doesn't hold water. This aligns the time zones and makes travel substantially easier for the majority of teams. The reason they gave for rejecting doesn't make sense. This was a good deal for the players. The alignment and subsequent playoff format was something they should have wanted.
So why did they reject it? Well the CBA is soon to expire, and the union knows the owners want this significantly. Instead of giving it to them for free, they want concessions (like protecting the salary floor). Rejecting the re-alignment will significantly suck for players on a number of teams who will have to spend more time traveling than they would have under the new system. The NHLPA wants this to be part of CBA negotiations that they get concessions for agreeing to. They didn't reject it because it was bad for players, they did so because it is a bargaining chip.