Cars on Blu-Ray Vs. Cars on HDTV

[djluis2k6]

Cars has an Aspect Ratio of 2.40:1, and it does have black bars on its BD release. Here's the question, why is it that they will keep some movies in their true Aspect Ratio on HDTV, while others, including Cars, will display them in full screen ratio? Does this mean that a full screen type aspect ratio was also made, or what? Because the picture isn't stretched or anything, it looks just as good as the Blu-Ray version looks with black bars.