> The real question is "On my block, what is the probability of any given house having at least one delivery on any given day"

In the city, I used to see multiple Amazon delivery trucks per day. On the rural road I now live on (dead end road with fewer than 30 households), USPS does most of the Amazon delivery, but this is somehow enough people that we see FedEx and/or UPS drive by pretty much every day in addition to USPS obviously driving by six days a week.

Given that they're also visiting the neighboring roads, it's definitely enough for an economy of scale.