IMO Do Not Safe Drop stickers can assist in reducing the likihood of theft from a residence if addressee is not at home to receive the parcel.

As the OP has found out however, they are not a guarantee that carding will occur, however my choice is to pop one onto my parcels, unless requested otherwise by a buyer.

In a recent Aust Post investigation over a missing parcel were compensation was paid, I believe that having advised Aust Post that a Do Not Safe Drop sticker was affixed to the parcel, contributed to being successful in gaining discretionary comensation, even though the parcel was tracked as delivered.