There's never any need to not attempt a delivery. If they miss the delivery by mistake, that's understandable, but with their route system, that would be nearly impossible.
Delivery people generally want to deliver the item as it means they meet their quotas and company expectations and in some cases they get paid per item.
It's bad enough being tracked whilst working, your every move scrutinised, never mind having unreasonable expectations from the consumer (not saying you are btw), but that's how it snowballs.
Over 13 years I got asked hundreds of times by the public when they'd get a parcel as they'd come looking for you, if you were on their round. Worst still was when you were trying to take a break as people think you're a robot and shouldn't stop until you're whole van of parcels and letters are delivered.
I think, when you've never done a delivery job it's difficult to have empathy towards what it entails and how pressurised you are and the further the public can be away from contacting the driver the better. Although a message to a CS call centre wouldn't be totally heinous.
The PDA's most companies use aren't infallible either. Once mine showed me in a different town and my boss asked how it was there (tracking my activity), so I sent him a photo of me on a street in the town where I was with my van partner, so the accuracy of "live tracking" is to be taken with a pinch of salt too.