Legally Blonde is the poster child for this discussion, whether you like it or not - it may be partly based on the novel, but its entire reason for existence is to call itself Legally Blonde and capitalize on that branding of the film. Otherwise they would have called it something else - certainly they would have forty years ago like Promises, Promises.
Whereas as Ragtime is NOT the poster child for this - it really was based on the novel and that movie was never branded in any kind of way, plus it was not really part of this outrageous thing that's been going on for the last decade.