There are still plenty of example use cases which aren't covered by the existence of QR codes and phone scanning. Documents which need ink signatures. Boarding pass backups so you don't hit disaster when you are running late for the flight and your battery dies. Government agencies which insist on doing things by post. Sending things to non-tech capable relatives or customers who don't know what to do with a PDF. Leaflets and handouts for community meetings. Notices which have to be physically displayed in a building or on a window. Homework assignments for young children.
Some of these you might be able to workaround with some added inconvenience (e.g. carry a spare phone battery). Others are simply impossible. I'm not going to fail to buy a house because I can't comply with the mortgage company's requirement to return a signed deed for example. Much as I rarely use my printer and wouldn't be bothered at all if it stopped being required, I accept that I need to be pragmatic about it.