That's right. There have been a number of times that friends who've come along with me to Disney will get a pincode afterwards. These people go very rarely, maybe once every 5-10 years. Those are the folks that Disney wants to entice with a discount, not the people who will reliably show up every year whether they get a discount or not.
Many people think of pincodes and other discounts as a reward for being a good customer. They're not (even though they're sometimes marketed that way). They're tools for modifying consumer behavior. For getting you to spend money you wouldn't otherwise spend. For convincing the infrequent visitor to book a vacation a little sooner than they'd planned. I see so many posts that say "I go to WDW every single year at Thanksgiving and I *never* get a pin! What am I doing wrong?" Nothing, but you've effectively taught Disney that they don't need to throw you any bait to get you to book a trip.