How did these clowns get everyone acting like trained fucking monkeys?
Because, for the most part, they are.
I don't think that it is about the "stuff" in general. It's about the social status of being someone who has the "stuff". The more in-demand the stuff is this season, the more social status afforded to acquiring it. Even if that status is only temporary.
Vendors want to see a repeat of customers fighting for their products. Whether it be an Elmo doll or a Cabbage Patch Kid or whatever. Be cool. Be the person with the stuff. Everyone who did not get the stuff will be so envious.