How bout you.. you know, actually use them?
Only ones really worth the use of an action point are the rare/legendary ones. The problem there lies in the fact that those happen to give the most reliable source of gold, meaning most would simply sell said cards in the hopes of rolling reward units from a booster pack.
Unless they get something like a War Theatre card, which deployment means more cards.
Tbf, non-reward unit cards on the market should either be deleted or reimbursed by a dev. There's little point in selling a card which is going to affect your entire team should it be used.
