In order to automatically keep track of all your purchases we need access to the digital receipts in your email. This way whenever you make a new purchase we can automatically detect it without any effort on your part. Without this you would have to manually enter the details of every purchase you made.* Linking your Amazon account is necessary to get access to all your Amazon orders as the email receipts from Amazon have limited information.
*This information is not available through linking your credit cards as they only have information about which retailer you purchased from (e.g. "Macy's purchase") and not information about the specific item (e.g. Nespresso coffee maker).