Thousands of people gathering in an expensive dedicated hall, to listen to the pathetic blatterings of a third-rate preacher, and the sub-par singing of their fellow gatherers. Most of them not believing any of the words spoken; indeed most of them not even possessing a conceptual model of what these words could possibly mean that they might believe were or weren't true. What are they doing? Communing.
Communing: the gatherers signalling that yes indeed they are part of the same tribe, that they may expect mutual support towards who complies to the tribal rules, and punishment to who transgresses. Tribal identification is not to be lightly derided; it is a very useful adaptation. Indeed, a tight knit tribe is necessary to defend against the harsh perils of nature, and particularly so against predators, the most dangerous of which being the two-legged kind. Signalling is a useful way to discriminate in favor of those who partake in the non-aggression and mutual defense pact and against those who don't, by being cheap to those who share the underlying mental structure being signalled, and onerous to those who don't. A shibboleth to distinguish the outsiders from tribe members. Being offensive or at least terribly annoying to non-believers is thus a verily intended feature of cultural rites, whether they are about celebrating the birth of the "lamb of god" promised victim of a human sacrifice, beheading your own sacrificial lamb to commemorate the willingness of some patriarch to subject his own son to a previous human sacrifice demanded by religious authorities, commemorating the military victory of some ancient gang of nationalistic religious zealots, or following the made up racist holiday of a communist fanatic.
But tribal identification and signalling of such don't scale to a greater civilization beyond an actual tribe. Obviously to all the annoyed witnesses who loath their intellectual inferiors, the conceptual baggage of superstition that accompanies obsolete rites is a hindrance to pursuing the benefits of modern science. But less obviously to this intellectual elite, tribal identification in a larger society is dangerous in that it empowers crooks who manipulate the masses: whereas the chief of a small tribe is directly accountable on his life to each and every tribe member that his actions would have seriously pissed off, a coalition of crooks that conquers Political Power over a large nation can make itself essentially impervious to any negative feedback from the people it dominates, and therefore largely unaccountable for its bad decisions, except inasmuch as it must keep doing whatever evil dealings it takes to stay into Power, or lose It to a coalition of less scrupulous crooks who will. Of course, that intellectual elite is the very class of crooks that seizes power over the tribal rabble that they despise, easily faking the primitive mental structures signalled by the rites, and manipulating the masses into subservience through their own, newer and more subtle superstitions. Which is why a self-interested double-thinking usually directs them to being quick at seeing and pointing out the "obvious" but secondary explanation, while at the same time being blind to the "unobvious" but more important phenomenon and directing attention away from it, intellectually superior that they may pride themselves to be.
In a greater civilization, the benefits of social cooperation cannot rely on a shared intent toward an identified common good; the transaction costs in building such consensus would be unaffordable. Rather, the alignment of interests amongst myriads of varied people it is achieved through peaceful market interactions, with price levels providing the closest thing to a distributed consensus about "social utility". Inasmuch as Civilization constitutes an extended tribe, respect for the Law is its entire purpose, as well as its tautological Shibboleth; members are not the citizens of a same City defending its walls, but the lawizens of a same Order defending its Laws. Unhappily, few have yet conceptualized the breakthrough of abandoning citizenship for lawizenship, and the existence of a "Natural" Law that could universally embrace all individuals in a common Order. Still, this Order is implicit in many of the behaviors that emerge in our current embryos of Civilization, and we must therefore rejoice indeed at how befitting it is that the Winter Solstice should have remained throughout millenia, and despite all attempts by religious bullies to take it over, a celebration of peaceful market interactions: voluntary giving to close family and allies of commercially acquired consumption goods.