I understand what you're saying, Steve, and for the most part agree with you wholeheartedly. I have ASF in my rodent colony only because I have a couple of adults that I purchased that will only eat readily on them, though I have gotten the one girl to take a rat on occasion. I have always said that I would never start any hatchlings on ASF, for exactly the reasons you have stated, however I did end up using the ASF to get a couple of hatchlings eating that had gone 5 weeks post-shed without eating....and they ate the ASF right off the bat. I gave them one more feeding one the ASF, and then offered rat crawlers, and they took right off. I may have gotten lucky, but would rather have them eating anything than starving.
I still wouldn't start them on ASF by choice however, just for the reasons you stated....they are not always readily available, and if I have to use the ASF to start them, I will always do my best to make sure they are converted to rats before sale.
I have, however, several times made the conversion to f/t for customers, and even had one occasion recently where the customer requested that I switch his snake to ASF from rats. If I have the time, I figure it's just that much more I can do personally to make sure the snake has a successful acclimation to his new home.
I understand all breeders cannot take the time to do this, and agree with what has already been said by others - if the breeder will not switch them, and you aren't prepared to feed what they are currently eating, simply don't buy them. Unfortunately, there are too many novice owners who may not know just how difficult making the switch CAN be. If I had an animal only eating ASF, and the potential buyer did not have ready access to ASF....I would refuse the sale, because as Shelly said, there is never a guarantee that they will switch.