Just because most advertising is abusive doesn't mean that all of it is. The popups that Steam shows when you open it are definitely still advertising, as are the recommendations for other games and things like that.

Ironically, this is exactly the reason why most other ad networks go to such lengths to track you, because they think they want to show you ads you'd find relevant and thus worthwhile to click on.

Unfortunately, the way the ad networks go about doing this means that they're actually incentivising making money by any means necessary over actually showing relevant ads, so you get ads that are psychologically abusive, full-screen ads that pop up in the middle of a game, ad networks selling off the data they have on you, etc.

That is why I will permanently have an adblocker - since this is how things work now - but why I don't care nearly as strongly about the Steam ads.