I order amazon on average once every 3 weeks. My mother (who has full time career and is under 60 years old) has never used amazon. Other members of my family also seem to rarely use amazon.
Also, having an order arriving every other day is incredibly wasteful.
If feels like there are Amazon households that get a delivery every or every other day and non-Amazon households that order 1-5 times a year (if that) and batch their purchases from other retailers (physical or online). That's the genius of Amazon. Those that use them, use them a lot.
I can say for certainty that Amazon delivers to my block every day. Adding 1 extra package is definitely more energy saving than me driving to Costco for the same thing.
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.