Actually that’s a myth (https://www.networkworld.com/article/2891297/the-myth-about-... ). Oddly, unlike most corporate founding myths (e.g. eBay and Pez) it wasn’t invented by company marketing.
There is a reason most grocery stores are shifting, or have already shifted to, Google or Microsoft for their cloud infrastructure.
it's a good point, yet many still use Amazon/AWS regardless. Netflix, for instance (AWS). Then, on the micro-scale: FBA[0] sellers (Amazon Marketplace).
I assume it has to do with the ultra low barrier to entry which Amazon/AWS provides. The convenience factor is off the charts. Nevertheless, I assume Netflix has ideations of following in Dropbox's footsteps.[1]
[0] "Fulfilled by Amazon"
[1] abandoning AWS for self-owned dedicated infrastructure
Via their multi-channel fulfillment offerings, you can already use Amazon's logistics network to ship your products sold on or off of Amazon. This would just be supporting more type of shipments than just fulfillment.
On the other hand, Fedex, DHL, UPS etc have built a big part of their strengths of shipping worldwide overnight. That's very different than what Amazon does, where they try to warehouse products close to customers to minimize shipping distance and time. Great when you want to buy an iPhone, but not suitable for shipping a document from New York City to Tokyo.