Source: https://bitcoinist.com/amazon-files-proof-of-work-patent-using-cryptography/
What is so clear with this development is that Amazon is working with the blockchain technology and experimenting how it can help in areas that it is concerned with. Essentially, they want the blockchain but so far not yet bitcoin as of this time. Amazon is pushing for the crypto but not the currency, as what the article above described this filing of the patent. Still, many are hopeful that soon Amazon can see the beauty of offering its buyers to use bitcoin.
Amazon doesn't care about cryptos and Amazon already has its own blockchain as a service