Probably enforcing the current laws on the books. But Auction houses seem to never follow. No transfers can be made at the auction they have to be done at the place of business. Even if the person has a buyers permit or carry license. And just because a gun is old and taken apart and junk the receiver still has to be transferred. I have seen this at lots of auctions that sold a gun as parts/junk without transferring. It has to meet the atf's wording to what they say is a destroyed receiver as to the cuts and how many of them.
I know several ffls that were told to stop doing these types of transfers and that the atf were going to start enforcing these rules and were going to start stings to catch them. So maybe the word is out.