That's not a problem in and of itself, except quite often I'll be leaving the house and there will be a package on the steps. I found it annoying that they couldn't ever knock loud enough for me to hear them, but I figured it was just that I didn't hear the knocking over whatever I had been doing in the house. This happened to my roommate a lot, too, whose bedroom is upstairs while mine is downstairs. We had been saying that apparently delivery guy knocks are a special kind that can't be heard anywhere in the house, because usually at least one of us will hear a knock at the door-- usually me. But we NEVER ever hear a delivery guy knocking, they always end up leaving the package. Not very annoyed at this point or anything.
Then today, I'm in my room. The window is right by the front steps (the top of my window is level with the porch) so I can hear things out there but not see. All of a sudden I hear a man chuckling and saying something I can't quite hear, coming from right outside the front door. I was and listen for a knock, but don't hear anything. I peek outside my window and see feet on the porch for a minute before I go head upstairs to the door. I open it and there's a package sitting there, and the delivery guy is walking away talking on a phone.
Apparently, it's not that we're not hearing them, it's that they're not knocking. Packages were shipped UPS or USPS always, though I'm not sure which ones these guys are usually from. This dude was USPS, but the same thing happens if it's UPS.