They're deploying it because the content companies demanded it.

Er, and why do you think that was? This really isn't helping your argument.

Your cited paper takes as an assumption that DRM works, and so is not evidence that DRM works.

It concludes by saying: "DRM is a valuable technological deterrent to piracy, and can improve a seller’s profitability substantially". If you don't class that as evidence that DRM works, perhaps you should review your concept of what counts as "evidence".