I would be happier about parcel delivery companies if they'd simply stop making up a delivery estimate beyond the date.
Let the driver use their local knowledge to plan the route.
Is my parcel coming on Saturday? — Fine, I'll stay home until the postie arrives.
Did you tell me they'd arrive between 11:37 and 12:43 and it's 13:30 at this point in time, with the live tracking disabled? — That annoys me to no end.