Indeed, it’s for assortive mating, which is a phenomenon of many if not all societies (even if the US press has only discovered it over the last decade). But then such systems are to preserve class status and power.

These cultural practices then serve multiple functions: one is to provide a common culture that makes such marriages work, another is to use values-based definitions which makes them both more flexible and yet more clear.

One point overlooked by this excellent article is the structure of the shift to highbrow culture. Before ~1900 the activities were not only expensive (e.g. the Season, the hunt) but were rooted in lowbrow culture as much as today (an aristo could reasonably participate in farm festivals, help with a cow with a breach calf, etc without loss of status).

The Bloomsbury shift to “highbrow” reflected the post WWI (relative) impoverishment of the elites: it didn’t require the extravagant expense of balls and states, yet still required (less) expensive education and leisure time. It could also be paid for by the state (as discussed in the article by the BBC, but also museums and such), something the elites had the right access to effectuate, transferring the funds from a broader tax base to their own benefit.

Probably sexual selection, but not just that. Many people like to have some basis for feeling that they're better than others - they're smarter, or better looking, or stronger, or richer, or a better cook, or something. Well, the elites have defined a game of social status (specifically status within their circles). This is a game at which they win and we lose. This lets them feel like they are better (literally "our betters").

But if you think about it, they defined a game where they not only get to write the rules, they also get (collectively) to be the judges of the contestants. And, no surprise, they keep coming out the winners and everybody else keeps coming out the losers. For everyone else, the only winning move is not to play. Let the "elite" play their narcissistic status game by themselves. Instead of trying to imitate them (and failing), find something real do and to be.