It's not stupid.
Unnecessary most of the time but it becomes an expected processing and delivery standard, which makes the experience much more predictable for consumers.
Very few can really compete effectively with Amazon on this front.
Source: Used to run an e-commerce company that shipped up to 2 million packages annually. Once we optimised shipping and processing, customer service inquiries and complaints dropped dramatically, and customer trust / sentiment skyrocketed.
My understanding is that in certain regions Amazon offers the option to consolidate orders to be delivered on a specific day. This is actually impressive as it's much harder to do at scale than you'd imagine.