The main protection is that the virus is not viable for long on inert materials.
So even if the packer was infectious, any virus that lands on the purchase or the packaging is unlikely to live long enough for the seller to get it to the post office.
It is possible that a package could pick up some virus in transit, but again the odds are that it would be dead by the time it gets to its next stop.
The one point of transmission has been covered by all carriers who are now refusing to hand over packages hand to hand. At best, the masked carrier will put it near the recipient, who then takes it inside. And no signatures.
EBay has confirmed that purchasing Signature Confirmation will be regarded as the same as having Signature Confirmation if Confirmation of Delivery is proven.
Enforcing a sanitation policy would be impossible, even ignoring those who refuse to believe the pandemic actually exists.
