Rated R movies are not where the money is

Last week on CNN Headline news in the midst of Katrina a brief segment was dedicated to R rated movies, and how they make way less than rated G movies. I then found this article reiterating that fact. This study said that Rated R movies cost more to make and make less than Rated G movies. There are 17.4 times more rated R movies made, but rated G produced 8.35 times more profits. Over 55% of all rated movies are R, with 3% being G; however that translates to R rated films making 11 million per film, and G making 94 million per film. With rated G films competively with the advantage, why doesn't major film makers shift their focus to family orientated films? Or is this happening already? For example, the Excorcist of Emily Rose is rated PG-13 (which made more than rated R movies also). Will the demand of G movies shift, or will it remain constant?