Cowans is primarily an antiques auction house with a very substantial antique arms operation. I have a very high regard for the guy who heads up that part.
Frankly, from their viewpoint, it is probably just not worth the effort to take the time to review every individual cartridge and headstamp to sort out the “good ones” from the large number of uninteresting ones. And. after many housrs of effort, they may indeed get a few more dollars for the good ones, but at the same time, fail to sell, or sell for less, the less desirable ones. And, for live auctions, where the buyers are mainly there for guns priced at $500-2,500 each and often a lot more than that, the added time spend on a couple hundred dollars worth of ammo may cause some hot bidders for the guns to run out of patience and leave. They will move several hundred lots in the course of a one or two day sale, and the seller’s best interest overall may be to get top dollar for the guns, and a bit less for the lots of ammo.
Of course, if anyone thinks they can do a better job handling ammo collections, they should start up an ammo auction service and see if they can make it worthwhile for their time needed to do it differently. That is not just the time of the cataloger, but also the catalog printer, the auctioneer, the billing and accounting people, and whoever does the packing and shipping. My observatin is that there are at least two very fine ammo auctioneer members of IAA that I know, and neither one of them seems to be in danger of getting filthy rich from their business, so this may be a niche service that pays off as much in the joy of working with the items as in actual profit from the business.
If anyone wants me to refer people with ammo collections to them for auctions, let me know-- I usually get several every year and would love to help them find someone who will get them sold for them. I look at the work involved and politely decline any involvement at all!