A concept you're missing: How about those of us who create graphics for Video, e.g. Final Cut Pro X.
We want a transparent background - preferably PNG, but we only get PDF option - to place on a Final Cut Pro timeline.
One track for the (transparent background) Pages' composition, on top of another track with moving video. Therefore, the video would show through the transparent background.
I can put the .pdf into PhotoShop, and use the Magic Eraser tool, but then I lose my "white type" in the Pages document! "White" is a preferred color for fonts on top of moving video. Even using a contrasting color wouldn't work, because of the areas inside of letters.
Pages is so much more fun to create graphics than PS. However, in FCP, supposedly we can import a PSD with layers, and each layer becomes a video track. I haven't gotten that to work yet. Used to 10 years ago, when FCP was more "desktop" than "pro".