At this point, I don't even think it's about the money - though that's a strong secondary reason. It's control. The MPAA sees people watching movies online as a loss of control that they have with the theater-cable TV-DVD/Blu-Ray model. They can dictate what theaters their movies play in. If they don't like a theater's policies, they can refuse to allow that theater to play the latest movie. The same goes for cable TV. They can decide what channels play the movie. If they don't like the channel, it won't get the movie. Then comes the disc-formats that only approved devices can play. If a DVD/Blu-Ray manufacturer steps out of line, the MPAA can send them out of business.
But releasing a video on the Internet in a standard format means that people can pretty much do whatever they want with it whenever they want. If I want to watch it now but immediately skip over chunks, I can. Without sitting through the FBI warning and trailers for "new movies" (that were released a year after this 5 year old DVD was released).
Losing this level of control scares them to no end and they'll wield all the power they can to retain control for as long as possible.