To add: The delivery company controls most of that, you will need to contact them individually. Each has their own policies over and above anything Amazon requires.
Deliveries in sketchy neighborhoods may require a signature even if the shipper does not or if the recipient has a history of reporting stolen packages and so on. Some companies offer a subscription service where you can sign online for stuff ahead of time.
Drivers have the option of requiring a signature as they go if they have concerns above all this.
NOTE: I do NOT speak for or represent Amazon in any fashion. This is a customer to customer forum.
Disclaimer: I have examined any sites I provide links for and have determined them to be safe but I make no promises about safety, content, ads served or anything that might make you clutch your pearls in horror. Use discretion clicking on links provided by total strangers such as myself.