The catch here is that players who use these cards often earn reward points for it as well as other perks.
If a player who has been loyal spends within $5000 - $10,000 in your casino but forgot to use this loyalty cards, if you were the casino manager will you still give them reward points for the expenses in the casino?
From what I personally understand, casinos hand out those loyalty card for a reason, and one of such reasons is because due to their large customer base, they are not able to manually recognize and reward players according to their level of commitment to the casino, so due to this, loyalty cards are handed out to players as a way to recognize and track their contribution to the casino, and subsequently rewarded accordingly.
If a player comes in to spend $5000 to $10,000 and forgot to use his loyal card, this amount of money is significant enough to earn him or her some reward points with or without the LC, so I see no reason why as a manager in such a casino, I should have a problem doing the needful.