I have no idea why they bother but the sticker on my post box and those of some neighbors were removed the third time now in the last 2 years. I know that they didn't remove them themselves because I talked with them and gave them new stickers. The kids in the house are either too small or to old to remove them so I can only assume it's the people distributing flyers. It sure is not the postman, he actually wrote a note asking everyone to put up those stickers because he didn't want to carry stuff that ends up in the trash anyway.