John Zhang of the Wharton School said that for businesses, digital receipts are “a cheap way to get your email address and to build their database to track your shopping habits. As a result, firms can do all kinds of targeted promotions on the cheap, and you will receive all kinds of junk emails.”
https://www.latimes.com/business/story/2021-03-02/column-consumers-paper-receipts-environment Los Angeles Times