Actually, I've been trying to put that one together ever since I saw it earlier today. I have no idea.

I've occasionally received letters with stamps that hadn't been canceled. I don't think the postal service cancels all stamps because people don't send letters as often anymore. Also, if I remember correctly, that package wasn't going very far (only about 100-ish miles -- I don't keep information on where packages are going, but I think it was going about that far). Maybe they didn't notice. Maybe it slid through.

Postal service isn't paying much attention.

Maybe the holiday-themed stamps had something to do with it. Probably not. I dunno.