Even with DRM, content can be stolen.
I prefer using widgets rather than videos because the widgets are interactive and they're generally smaller in size. From my experience on the App Store, I found that I would lose sales if my app was too large. Lots of people don't have a lot of space on their iOS devices.
So, when I made A Book About Hype, I focused on keeping the book lightweight.
I deleted some extra files from the widgets, but that was mainly to keep the file size down. With an iBook, I don't need to worry about IE 6-9 support.
It is a tough problem, but I think it's getting better for publishers. With all the hacking, viruses and ransomware, people are better understanding the downsides of illegally downloading digital files.