Costco can only fill maybe half my pantry because they don’t carry everything I like to eat or use regularly.

They do a form of cherry picking the easy high volume stuff, and let other retailers deal with the harder more expensive low volume products.

Certainly useful to optimize their bit of the supply chain, but they only can really account for maybe a quarter of the food items we eat, which accounts for a third or maybe half of total product volume any given month. The rest needs to come from additional store runs or Amazon.