It would be cool if a manufacturer or dealer offered a "certified ready" program guaranteeing that the unit is in excellent condition and ready to go.
I would expect that a PDI would indicate the unit is hooked up, refrigerator running, a/c on, furnace ready, water tanks filled, so that the new owner could try all the systems.
It's a highly unregulated industry and I doubt rvers would tolerate the same conditions while purchasing any other big ticket item. We seem to want to protect and justify our hobby from the truth in purchasing, in many cases, junk off of an assembly line.