It's obvious that bulk shipping some items is more efficient than individually shipping items. If there's enough demand for an item to ship it by train car, boatload or, truck load to an area, the cost of that shipping will be fractional to the cost of UPS / USPS / FedEx delivery. Bulk staple items like bottled water, toilet paper, paper towels, sodas, milk, laundry detergent, etc are just not good targets for Amazon.
With curbside pickup at Walmart, Target, and grocery stores now, it's arguably easier to stop by the store on the trip home and load up those items. Cuts down on packages left outside your doorstep that can be stolen.
Amazon just needs to rebrand this brick and mortar process. Call it 'AI PreShipping', Amazon can leverage their AWS power to analyze regional shopping characteristics and PRE-Ship your items to your convenient PRE-Ship Storage Location (re-branded from Whole Foods). As your Pre-Shipping items will be stored at our facility, rent will be covered by your Prime Membership.