Photographs. Shopping lists. Airplane boarding passes. Printable coupons. Signed documents that need to be mailed in. Hard copies of your tax return. Instructions for a fix-it job that you need to take outside. A million other mundane things.
They all or mostly CAN be done on your computer or phone, but many are better to have a paper copy. You know how freaking slow an airplane boarding process would be if everyone used their phone? Do you really get by without printing ever?