Disadvantage for the seller: Customers usually don't have a proper PGA puller, and it's more than likely that the board is mechanically damaged before the customer can make the first test run. It'll feel like "dead on arrival", and the customer will blame the seller.
Seller must give warranty because it's hard to prove that the customer made a mistake. Even if seller proves that customer made a mistake, customer will be p*ssed and badmouth the seller in forums.
Result: Cards without CPU will be more expensive than cards with CPU.