You know, with something like the Wallpaper Engine existing on steam I'd have thought that some stuff would be uploaded, but there really hasn't. A lot of quality stuff can be done w/ it once you work your way around it. Conversely, I say this but I also know a lot of people would use it to make potato quality content given this site's track record.

In summary: A lot of potential can be had from it, not sure why no one of the fetish has done anything w/ it.

I'm not familiar with the program at all, how would one go about producing MC stuff with it? From what I read on Steam, it's mostly just about animating images, or is there more?

You can use any mp4 or gif file, or make an animation in Unity. It's really easy to use. I have it on my gaming PC, and it's really cool.

Also to answer the initial question:
It's because money. The program costs $4.99 or something like that, which most people won't spare.

This sounds like something that wouldn't be allowed under the mass producible image rule.