Why bother actually trying to do the work of translating a beloved property to a different medium? We can just use a known title to sell people a completely different story, and it doesn't even have to be any good!

See: Eragon, The Princess Diaries (especially Princess Diaries 2). That sort of disregard for the genius of the original work seriously pisses me off. (Well, maybe not "genius", but those books were rather good in their own right. And then they made them into movies.)