I believe all of them have it because of its durability for handling large amounts of torque, and certainly durabilitiy is a strong point for it. It's important to note that the transmissions in those cars have COMPLETELY different programming. The programming is the big problem here. Are you saying you are completely satisfied with the STOCK performance of the transmission that came with your SRT8? I obviously am not.
If the 5-speed is so outdated why do the following extremely expensive vehicles still use it?