[CardenB]

People don't usually drive to the store every single day for a single item, whereas amazon would deliver a single item to people every single day.

[manigandham]

That same delivery vehicle can service 100s of homes at once though, which is why it's more efficient regardless of 1-day delivery windows.

I'm sure they could do a better job of batching deliveries for a single drop off per day but I don't think that's as bad as it might seem considering the overall reduction in consumer-to-store travel.