DRM enables content creators to get paid
There is need to control at least some of the content some of the time, or piracy rates will get so high that content owners cannot stay in business.
DRM enables new business methods
Having content in digital on-line form, in conjunction with ubiquitous Internet access, creates many opportunities for creative content businesses. This has been true for some time, but only in a few cases, like iTunes, has it been taken proper advantage of.
DRM can help save history
If I have truly acquired a RIGHT to content, as opposed to a physical medium containing the content, then there is the potential for one to get that content anywhere, anytime, in any format required by evolving technologies.