Recall Vick Kelly's adjustment for couples of the Tomkins blueprint for individual wellness---1) Intimacy requires that people mutualize and maximize positive affect and 2) mutualize and minimize negative affect. 3)The system works best when we are able to express all of our affect to each other; and 4) anything that assists these three rules fosters intimacy, while anything that interferes with them impedes intimacy.
Alcohol reduces shame. We know this from sayings like "in vino veritas" (in wine there is truth), and our own individual experience "drowning our sorrows" after rejection. Shame affect is triggered by any impediment to positive affect, and as an amplified analogue of what has triggered it, shame affect then goes around further impeding the experience and expression of positive affect.
Therefore, having a drink together allows a couple to "celebrate" in the sense that their access to positive affect will be greater than when completely sober. The degree of intimacy afforded by this manoeuver is pleasant but transient; often people will be more than vaguely embarrassed by "what we did when we were drinking last night" because the intimacy experienced in such a situation may be greater than really fits the stage of the relationship at the moment in question. It is, of course, possible that people can use alcohol to overcome the mild shame-laced blocks to new intimacy and then enjoy their new relational territory, but every new territory must be explored together.
In short, then, the recreational use of alcohol can produce an experience of shared positive affect, although the meaning for the relationship is variable. If the relationship becomes dependent on alcohol for access to positive affect, both the relationship and the individuals will get into trouble later.
But hey! Roz and I own a vineyard. I'm the wrong guy ever to think of as against the pleasure of a good glass of wine shared with one's special friend.