Underbody Shield problems of the 2003 Mazda Tribute

I have a 2003 Mazda Tribute v6. After taking the vehicle in for a recall, they noticed that my front passenger side subframe was rotted. The drivers side is fine. The exhaust goes thru that area - it appears that the heat from the exhaust caused the paint on the subframe to 'burn' off and thus allow it to be exposed to the elements and rot. I have read other cases of this same thing happening to other people with this vehicle. There are other manufacturers who have recalls on this same item for their vehicles - why doesn't Mazda? it is not an easy or cheap fix!.