With that said, come on now, what exactly do you think people who are purchasing old giftcards in bulk are doing? Decorating Christmas trees 
?
Could be! People buy all sorts of stuff for no obvious reason.
I used to get thousands of Monopoly game tickets (from the Albertson/Safeway annual promotions) because of bulk buying of gift cards there. You have to open each one up to see if you're a winner, and the rewards were things like a free doughnut or 50 cents off a quart of orange juice. Most weren't winners. It was a waste of my time to open each one, so I sold them on eBay and got about 35 cents each for them before eBay decided that it was illegal to sell such "lottery tickets" and banned their sale. I have no idea what the buyers did with them.