I don't dont think its generally that deep. Most people like to party, and the "marriage send off" is generally considered a wildly bacchanal one, if not outright hedonistic, at least for everyone else attending.

The intended lack of inhibitions probably does cause issues to bubble up, and it honestly likely ends relationships that probably should be ended, even if the people involved won't acknowledge that sober.

I also wouldn't be surprised of it is used as an escape hatch by some, perhaps by "unintentional" behavior that can be blamed on the party itself.