What do you get with the dunkin donuts points? I'm assuming, it's at most something like a $5 sandwich or something. But for 63K AA miles you can get a CX first flight that sells for thousands.

Donuts and coffee are "luxury" items, often bought on the spur of the moment. People probably think, oh, I have enough points for a free coffee. While they're there, they get a donut. Or a breakfast sandwich. And they feel better about themselves when buying coffee there in general, because they're getting points even if they are spending money. Even if the points are worth very little no matter how savvy the redeemer is.