Comment Theaters broke & wary. Plus more on DLP techno (Score 2, Informative) 536
Small Times just ran an article last week on this same thing. There's no distribution cost to the studios, while the theaters are the ones who pay for the cost of the upgrade. Another problem? Theaters switched to digital sound systems in the early 90s, and that didn't pay off for them either.
If you're interested in more information on the technology behind DLP check out the Small Times article.