Actually in some breeds it is required that a seller send in the transfer. Here in Canada any horse that is advertised as purebred must be registered with one of the CLRC affiliated registries--and all CLRC registries fall under the Animal Pedigree Act, which specifically states that seller must send in the transfer and provide buyer with the registration papers in the buyer's name--within 6 months of date of sale. So, when we had the Morgans that's the way it was always done--and seller is not legally able to charge the cost of that transfer to the buyer. A horse not registered with a CLRC registry must not be advertised as purebred, and does not fall under the Animal Pedigree Act & so sellers are not required to do the transfer. An American Saddlebred, for instance, without Canadian papers must be advertised only as "ASHA registered Saddlebred" rather than "registered Saddlebred" or "purebred Saddlebred".
I have bought Minis where the seller did the transfer--in some cases seller paid for the transfer, in other cases I gave the transfer money to the seller & she sent in the paperwork, and then provided me with the papers in my name. I have done the same thing--sent in the paperwork at my expense, and at least once have collected the $15 from the buyer & then sent the transfer in myself. Buyer wasn't a member so appreciated getting the papers into her name without having to buy a membership. and other times have just handed over the signed transfer and the buyer did the paperwork (and I as a buyer have done that too). I would never think that a seller is crooked just because she/he offered to do the transfer if I weren't a member! (As I read it earlier, Margot did offer this person a choice on how to do the transfer.) A simple 'no thank you, I prefer to do that myself' should suffice--no reason to get huffy & cancel a deal because the offer was made--now if the seller absolutely insisted & wouldn't sell the horse any other way, that would be another matter.