The two piece driveshaft on our 05/06 cars just can't be necessary. Why did Ford go to this much expense making a driveshaft this complicated and heavy to boot? Surely a one piece lightweight aluminum would have been equally as good and given the car better fuel economy.

Probably the same reason GM did it with a couple of their cars - noise and vibration control.

Yup. Noise and vibration.

But for GM, why they used it on V6 cars and not V8 cars though, I don't understand. *shrug* Kind of dumb if you ask me being they were both the same lengths, haha.