The strongest model I have for understanding the world is that your prefrontal cortex is a simulator that is always predicting. When something occurs that surprises you (like a glass breaking in a restaurant), the anomaly diverts your attention to the sound source so your visual system can feed more data to your model and rationalise the event.
But when something happens that contradicts your model, it means your model is wrong, and this causes severe anxiety (cognitive dissonance). This explains why people get more upset when things don't go the way they expect than whether or not things go badly or well, which is why managing expectations is such a high priority for project managers. It also explains why autistic people who struggle to abstract and get upset by social disappointment rock themselves: to create a signal they can predict. Otherwise, the bottom of your world falls out every time someone moves their cheese - like a baby throwing a tantrum when they drop their favourite toy before they have a model of gravity.
Now, why would people want to get drunk together? I think we want to test congruence and resilience in a vulnerable situation. The better a person can predict your social cooperation in a variety of contexts, the less bandwidth they can afford to devote to modelling your actions, which might otherwise pose an existential threat. Once you have mutually compatible models of cooperation, you can safely turn your backs to each other and work on solving external problems without causing internal anxiety.
But being predictable also means you are vulnerable. If you can be modelled, you can be manipulated. So we crave a certain "predictable chaos" from our friends, partners and co-workers. We want someone self-aware enough to follow the rules, while pleasantly surprising us in ways that expand our mental territory without invalidating too much of the existing foundation. A quick way to upset a drinker is to turn down free drinks at a bar at night (but not in the middle of the day). It forces them to re-evaluate their model of the world - and, people hate doing that, especially drunk people. The same is true of questioning people's religion.
Incidentally, this is also why you dream and have nightmares, and seek out horror movies when things feel stagnant. Your mind is exploring your survivability in a bunch of threatening situations that could arise, and learning from them without dying.