Well it might depend on the size and value of the 'piece of paper'.
For example, the seller of this item, 351498732626 , might want to use extra bubblewrap and maybe some insurance and tracked delivery.
Or it could be an error on the part of the seller.
Or the seller might want the exposure of his item in Search that he gets for international selling, without the actual "problems" of shipping internationally.
If you really want to know, you can use Contact Seller to ask.
If it is an error the seller would probably be grateful for the headsup.