At the end of the day if the buyer has to pay their agent that is just a lower price they can offer you. Also it means they can't roll the cost into their mortgage effectively financing their commissions. So likely the amount they could offer you would be substantially less than just the cost of the commission. Allowing buyers to finance the buyer's agent commission by having the "seller pay it" means it can be rolled into their loan, and they don't need the extra cash.