To be clear though, these "ads" are solely for Microsoft/Windows features, the most third party they get is being "suggested" apps on the Windows Store. Some people may not perceive them as "ads" (and Microsoft claims they aren't, as laughable as that is), because they are connected to Windows features, you'll never get sent to a third party webpage from these things.
And I don't think they're actually paid ads, for either the suggested apps or the rare occasion they've put an "ad" as the lock screen background. They've promoted the Surface on it before, and then for Tomb Raider, I think they were mostly pushing the idea of "hey, you can get games in the Windows Store now", rather than it necessarily being a paid campaign with the game studio.
And I don't think they're actually paid ads, for either the suggested apps or the rare occasion they've put an "ad" as the lock screen background. They've promoted the Surface on it before, and then for Tomb Raider, I think they were mostly pushing the idea of "hey, you can get games in the Windows Store now", rather than it necessarily being a paid campaign with the game studio.