Not the best, I agree. Only takes a few seconds more to knock or push the doorbell.
I'm usually at my computer or have my phone with me.
I always get a text or email shortly after they scan it and leave it (same with Fedex....USPS sends one too, but it seems like it arrives delayed later in the day/evening).
I've heard that they are required to deliver everything on their truck before they end their day (except signature required items) and that they are monitored via GPS. (true or not, that's just what I heard).
I'd 'guess' a large majority of recipients are not home anyway. (If UPS knocks on a tree in a forest to deliver a package, and no one is there to hear it, does the knock make a sound ?)
Personally, I'm "OK" with no doorbell or knock, as long as I get the text/email.
If I got 'nothing' to say it had been delivered, I'd have an issue then.
...but that is just me.