It is not okay to abuse someone just because they can ask you to stop.
Particularly when you can easily disable them. No other game client I know of offers that.
I'm very anti-ad, but if there's one situation where I don't have a beef with it, it's the Steam app.
On the other hand, I don't classify what Steam is doing as advertising. When I open the Steam store, it's because I want to see the games it has on sale. It's not advertising, it's the exact information I asked for. It would have been advertising had it kept spamming me with game deals while I'm watching a film or something.
They don’t force themselves onto your machines mate.
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.