Thanks to chocolatepot for linking to some of my previous answers. The TLDR of it is that it was considered bad manners to be drunk in public. One of the foremost signals of a cultured life was diluting your wine. Wine was seen as a catalyst for social discourse and getting overly intoxicated could certainly hamper that aim.

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It looks like this question's been addressed before: http://www.reddit.com/r/AskHistorians/comments/1g2ps4/what_is_the_difference_between_modern_day_wine/

Specifically down here: http://www.reddit.com/r/AskHistorians/comments/1g2ps4/what_is_the_difference_between_modern_day_wine/cagb9zc