DRM, that is Digital Right Management, is actually three evils in one.
First of all, many publishers view DRM as a way to manage (read increase) their rights while reducing the rights of the consumers, i.e. restrict the resale, activation limits, remote killswitches etc.
Secondly, many legitimate consumers find DRM annoying - they purchased a product but cannot use it as they see fit - be it that cannot transfer their music CD to their MP3 player, or play that game without contacting the publisher's master server.
And thirdly DRM is an excellent excuse NOT purchase something, but rather obtain it illegally. After all, stealing from a "nice company" does feel wrong. Screwing some corporate morloch that does its best to screw you feels much less wrong.