I don't think you understand what you are seeing are advertisements. The blades had ads too, occasionally. Just a banner ad for a new game or something. I'm sure you saw them. NXE is that times 10. Ads for games, movies, random shit people paid them to put up like Subway.
They have 3 channels devoted to nothing but advertisements: Spotlight, Inside Xbox, and Events. Of course there are tons in the Marketplace and Netflix as well, though those at least are slightly reasonable since you should be advertising in a sales section.
All of this is nothing but useless intrusive clutter. It makes it harder to navigate to the things that matter. Do you not consider a banner about buying a game on gamefaqs an ad? This is no different. There are just a lot more.