The US Postal Service is using algorithms to estimate the tracking of packages instead of reliably scanning the packages that have tracking/delivery confirmation.
Why? Because in the past three months I've had packages arrive in my mailbox a week after they said they were delivered. As a seller I've had customer's packages with delivery confirmation show as delivered that didn't arrive until days later.
This absolutely sucks for consumers who don't get their package but have no course of action because the PO says it has been delivered.