There was a whitepaper that Amazon published like....5-10 years into their market dominance where they shared how they wanted to get into drone-based delivery because the vast majority of items purchased on Amazon were very light-weight items.

This tracks with me. The problem that Amazon solved (at least for me) was the ability to find small items that are near impossible to find in a Walmart or other superstore. For example, say you are looking for some wax for your car. You go to Walmart and you see a wall of products. Now did they put the wax in the right place or did they put it with the cleaning stuff? You spend 20-30 minutes looking for this one item that you're not going to buy again for maybe a few years when you can go on amazon, find it, buy it, and have it at your door in two days.

Walmart and other stores have gotten better with their apps but they need to do what Home Depot/Lowes have done and do aisle AND bay, and, ideally, where on the shelf to find it. They already have this information but they don't want you you to exactly know where it is because Walmart wants you to browse.