Apparently, a group of reasonable, relatively responsible adults, without a unanimously recognized authority figure and in the presence of a veritable mountain of colorfully wrapped gifts (and under the influence a not insignificant amount of alcohol) will utterly lose any shred of self control and rip into their presents a full two days early. Not for any reason other than proximity and desire.
It all started out reasonably enough. Debates on the tradition of Christmas itself, the arbitrariness of a date selected by a religion none of us actually follow, selected largely as a convenient way to convert pagan contemporaries. The futility of waiting. The extra time to play with our new toys. But what it boiled down to was the number of cocktails. Pass a certain number and the wrapping paper basically falls off the presents of its own accord, and then what can you do but indulge?