Good point. For everyone who actually wants to check the receipt at the POS there is an option to also receive a paper receipt (i.e. email and paper). If the receipt is ok, you can throw away the paper receipt and keep the email receipt for potential future changes/returns/expense claims etc. Now this defeats the environmentally benefit of email receipts but is a way around it. Some retailers let their customers look at customer-facing till screens while scanning the purchase items.