Why they are pulling these lucrative movies from circulation is only speculation at this time, but considering that they have grossed over $12 billion, it might be a bad choice. However, Disney seems to succeed in doing this when they offer specific movies every once in a while for a limited time.
Perhaps it will be like candy corn and shamrock shakes, the fact that they are a limited offer will increase sales when they are around. Regardless, you have through Christmas to get your movies, for sure!