Because paper still needs to be used. I have customers that request paper invoices. I send them paper invoices so that I get paid. I have vendors that have no means of accepting payment other than by check. It is a lot easier to print out a complex troubleshooting or repair guide to use at a remote location than by trying to balance a tablet in some dark corner of a boat. The IRS still requires paper forms to be mailed to them. The local ferry system requires you to present a reservation sheet with its barcode and the ticket printed with its barcode. And the list goes on and on. My business is substantially digital, but paper is still required.