The Gimley Glider was just a few years old and was one of the first B767s out, so it was definitely cost effective for it to be repaired and returned to service.
This, on the other hand is a different story altogether. The report says one of the youngest B767s in AA's fleet. But i would guess it's at least 5 years old since it's just came out of HMV. And with the current economic climate, it would not be cost effective to repair it and return it back to service.