Our postman is good, but other delivery services (including Parcel Force) are much less so. Like others, we have a doorbell, but they never use it. Some bang on the door as though it's a police raid, then scoot off down the path like the hounds of Hell are chasing them. By the time I get to the door they have usually driven off and left the parcel on the doorstep, not knowing whether we were in or out. I've had items left for days as they arrived long before we were advised when ordering. Others have arrived late and we've gone away, so again they were left unattended and in view of passers by, despite the fact that I always ask for them to be left at the back of the house.
Considering the cost of postage these days, the least they could do is make sure that parcels are actually handed to someone, and not left unattended unless the courier is given express consent to do so (and then they should leave it where instructed).