They may have a similar setup as we do. Some parcels must be signed for by the sender's request. Others instruct us to leave the parcel at the doorstep even if there is no answer. It depends entirely on what the sender paid for, at least with us. Next time you get a package that you did not have to sign for via UPS, call and find out if a signature was needed. It would be a quick way to see if they are signing on your behalf.