Almost a page full of mostly ........
the reason are simple, for the educated.......
-the duck has only ever been competative for one rider, hence it's development as a more all round package has still some ways to go. Rossi, at this stage of his career doesn't have the time or the patience for such an undertaking
-rossi is currently riding arguably the best all round package in motogp, which he had a very large hand in developing. Apart from his four world titles with Yamaha, rossi also has a great working relationship between himself the team and the manufactuer. Ducati is know for being Honda-like, so why go backwards?
-riding for an Italian manufactuer certainly doesn't dissuade vr, those of us who have been around long enough will remember 1997 and 1999, when vr won his first two titles on an Italian bike. I dare say that if aprilia were in motogp with a competative machine vr would be more tempted to go that way based on his history with them and IMO they would build a much more user friendly package.