airbourne
I don't see you're logic. You can still fly one route with DL and have a completely different experience on another. Why does fleet size have anything to do with it. The passenger doesn't take that into consideration and wouldn't always believe that it should be. Plus we both know that DL has a huge domestic fleet that we can take out of the equation here.
When VPort was launched for example, the LGW 744's were still relatively new so why replace them there and then? Refurbishment, admittedly, has taken longer but again there are still airlines where you get a PTV on some long haul sectors but not on others. PTV's being just one consideration of the hard product of course.
I'm not necassarilly saying it's right or certainly not ideal but is it a disgrace? Probably not.