This kind of thinking is largely a fallacy these days though. Most piracy is casual in nature these days. We're not in the days of people burning disks for friends anymore, the public at large is a lot more tech savvy than given credit for and I doubt most people even use the dvd drives in their computers anymore.
A more simple consideration is does the bad PR from DRM outweigh other considerations? Ubisoft obviously seems to think so but I doubt their reasoning is rooted in any logical rationale. There are more sane approaches to DRM that other companies employ successfully without impacting consumer experiences to this degree.
Interesting tidbit inc... A pirated copy of From Dust is available, but not one for Deus Ex : )
I imagine there are many factors at play, but it is interesting from a quick-look point of view.