I also think that package theft is reasonably rare - to the point that retailers are willing to put up with it and just re-ship the packages. I live in a major city and in a decade I've never had one package be taken (at 5 addresses in different neighborhoods). Personally, I wouldn't want them to attempt re-delivery for days and then tell me to come to their service center to pick it up.
Companies like UPS and Amazon also have options if you're worried about theft. UPS can leave it at lots of convenience stores for pickup. Amazon has their lockers all over the place.
Still, given that I've never had a single package stolen including shipments of laptops and such, I don't really want to have to travel to pick up my package.
The person sending the package can choose if the package is left at the door or if it requires a signature. Amazon and others like them have decided that the increased convenience is worth the occasional cost of reshooting a package.
Most of the country is somewhere between here and "thief follows UPS truck and steals all unattended packages," but there's lots of places where leaving packages unattended makes good economic sense.
Also, I'm not sure how it works outside the US, but here frequently packages with higher value items will require a signature and therefore wouldn't be left on a porch.
One option is to have the package delivered to the work address, or if you live in a building with a reception, the receptionist receives the package for you.
(Also, where I live a house's porch is normally behind the fence, so to leave a package in the porch it would have to be thrown over the gate.)