I live in a resort area that doesn't have many full-time, year-round residents. Every year we have issues with FedEx saying they attempted delivery but no one was home, even when people are sitting at home all day. While we can't prove it, what appears to be happening is that either the local warehouse is waiting for multiple deliveries before they send a driver to the area or the driver is just waiting for more than one delivery before he comes to the area. It only happens with FedEx and I would assume that it has more to do with the majority of their ground drivers being independent contractors.
I don't know about the US, but drivers here are paid peanuts and being contractors they'd actually lose money to make some deliveries.
In other words, parcel service companies are well known for being economical with the truth.