There is literally no reason to put a cap on using the codes. It just means people are buying and opening tons of packs. Reselling the codes will never be profitable for the sellers so it doesn't matter if they try to do it. Maybe it'll cut into their profits on the digital thing but as previously pointed out, those are already overpriced anyway.
Western F2P game devs don't understand that free to play games need free to players in order to have a population of people for the premium players to play against, so the F2P economy has to be minimally viable for people who are determined to never spend a dime on the game.