Documents are two way streets. You need them to prove your rights. You need document to prove your identity to bank or notary. If you are younger side, document helps validate your age in liquor store. I trying use "american" examples here, but other countries can have other regulations or customs. Document, especially digital one, is very useful. For example, I like do encrypt with id card, when sharing materials over untrusty medium. You don't need worry about key exchange, you don't need to teach or install software to other party devices: they already have knowledge, how it works. It's also very comfy that I can send digitally signed documents and that isn't fringe thing, there is knowledge and bureaucratic processes, how to handle it.