I think the drivers sometimes get lazy and decide to make up excuses on why they can't deliver. A couple weeks ago I had ordered something to be delivered same day -- I paid the extra $2.99 for rush shipping. I kept waiting and waiting past the promised time... finally I got an alert from Amazon saying my delivery had been delayed due to the driver not being able to access my front door. Wtf. The only thing I could think of is I had already put out my garbage can for pickup the next morning and it was blocking a VERY small section of my driveway, which could have prevented them from pulling their truck into my driveway.
Here's what I think happened -- it was raining the entire day, so when they saw they couldn't pull into my driveway to get closer to my door they made up fake excuse. The street is literally ~25 feet from my front door...I guess that was too far to walk in the rain.