After all how often do you/we get unexpected deliveries?
If an on line purchase is made - it can be tracked- and you do know it is coming and by what service.
If it is an 'over the counter purchase' the buyer would check with the seller.
If it is your birthday- your rich aunty/uncle would tell you to expect a something would not they?
I have all of these from time to time- all go to the bin without hesitation.