Ian Hickson, the googler who is overseeing the HTML5 standard at the W3C, has written a surprisingly frank piece on the role of DRM. As he spells out in detail, the point of DRM isn't to stop illegal copying, it's to stop legal forms of innovation from taking place. He shows that companies that deploy DRM do so in order to prevent individuals, groups and companies from innovating in ways that disrupt their profitability:
The purpose of DRM is to give content providers leverage against creators of playback devices.
Content providers have leverage against content distributors, because distributors can't legally distribute copyrighted content without the permission of the content's creators. But if that was the only leverage content producers had, what would happen is that users would obtain their content from those content distributors, and then use third-party content playback systems to read it, letting them do so in whatever manner they wanted.
Here are some examples:
A. Paramount make a movie. A DVD store buys the rights to distribute this movie from Paramount, and sells DVDs. You buy the DVD, and want to play it. Paramount want you to sit through some ads, so they tell the DVD store to put some ads on the DVD labeled as "unskippable".
Without DRM, you take the DVD and stick it into a DVD player that ignores "unskippable" labels, and jump straight to the movie.