Two sets of Screenshots - Play Store Why does every app on the Play Store have two sets of same Screenshots?

Some apps have Portrait and Landscape Orientation Screenshots but most of them have the same Screenshots twice.

Is it some sort of bug? Or is there some real purpose to it?
When it has two sets but one is landscape, that shows what it would look like on tablets, screenshots in portrait are from phones.
And about that when there is 2 or more sets of screenshots in same orientation, I think the uploder do that, don't know why, maybe because of look when there is only 2-3 screenshots, but even when having enough screenshots, I don't know why they do that.