Remember this is a WELCOME drink, not a bar round; you can get whatever drinks your want after take off. And you've just been in the lounge with all manner of drinks. If everyone makes a small request for a water or AJ or Coke, then suddenly a quick drink before the doors shut becomes impossible for the crew to accomplish.

Not to mention, this is an obvious differentiator between Club and First, when people are very quick to say the cabins are too similar.

There's enough for everyone to have one bottle of water, but not enough for everyone to have two (unless the cabin is particularly empty). The crew are more than happy to refill the bottle you have finished though.... They're not single use!