Don't get me wrong, I don't think drinking is evil. After all, as a Roman Catholic, wine is an integral part of our Mass. I just don't understand some other Christian perspectives on this miracle.
Perhaps in many locations the water needed to be purified to drink. Wine could have been served to the entire family. That is the same reason that beer was the primary drink for the English, the water (alone) could kill you.
We have been taught: moderation in all things. Overindulgence in pure water can probably kill ya, or make you wish you had died.
Merry Christmas. :-)