My best description is that the "cost" of inconveniencing a customer (e.g. limiting device playback, etc.) will never really meet the goal of protecting content. This is because those who want it for free will always find a way to get it (at some "cost"). Those who don't have time/don't give a shit, will pay for the content because the opportunity cost of pirating something is greater than just paying for it.

That said, i find it really annoying as a parent to have to jump through hoops to make backups of my kids DVDs, or convert them to digital for the iPad. So, I'm not stealing anything as I already bought the DVD. I just want my kids to be able to watch it on the iPad.

I don't know of any DRM that "provides a benefit" to the user.