I wonder why they don't? Whose idea was it for that stupid cheesy movie? Glad they don't try and do that any more. Oh, and I sure won't be watching that Fantasia bio.
I think the idea was Simon Fuller's, maybe with Nigel Lythgoe's input. Fuller's the originator of Pop Idol in the UK and AI here. I think they were surprised by the success of the first season and saw the movie as a quick, cheap way to capitalize on it. Justin and Kelly didn't have a choice in the matter. Due to provisions of the AI contract, they had to do the movie, although neither of them really wanted to.
It was cheesy from start to finish. The script was thrown together in two or three weeks, and it was filmed in a very short time using lousy production values.