To add on to the ad point:

General purpose ad markets do this in your everyday web experience, but the process is less noticeable because the bidding pipelines are wildly optimized and the pool of bidders to pull from is much wider. Besides this, the profiling data your browser has on you is much richer so it's easier to dump you into a particular funnel. These are systems built and maintained by people who only care about landing an impression in your eyeline as fast as possible because that's the only way to get paid.

Steam, Epic, whoever does not have an adtech team, or if they do then they're a handful of people attached to a larger analytics organization. The primary product is the storefront, the advertising is just there to keep you on the platform engaging with things. I would not be shocked to find that there is no bidding system and they are literally just iterating your list of owned games and serving ads for "whoever is currently paying us to promote their game" + some random stuff in the orbit of your existing library.

This is why the ads both suck technically (blocking UI paints, fucking page layouts, broken links) and functionally (incoherent stacks of ads, AI spam, genre soup): effective adtech is an entire subfield sucking like a lamprey on the belly of any sufficiently large content aggregator, but if you don't pay for talent you get shit.

Gamers as a consumer bloc barely need advertising because most of the money is in live service games which already do traditional advertising (and therefore only need a buy button in a prominent place on the storefront) and all the rest of the usual "word of mouth" is handled by the gaming press. Truthfully, what's the most memorable ad you can think of for software? Infinitely replicable products don't need advertising, they just need a smooth purchase experience. Physical goods and services "need" advertising because you have to get off your ass and talk to somebody to actually give them your money.