This was copied directly from UPS's website.
All Tobacco Product Shipments must be made using UPS Delivery Confirmation Adult Signature Required service, requiring the signature of an adult 21 years of age or older upon delivery. Federal law imposes labelling and packaging, record-keeping, and tax-collecting obligations relating to permissible tobacco shipments.
This rule has been in effect for over 30 years.
Both UPS and FedEx have a "sign one time for all deliveries form" of which I signed 30+ years ago.
It covers all deliveries of any type.
With certain exceptions (pricey items etc.), this allows them to leave a package without getting a signature, tobacco products included.