Not the parent, but I agree with them: Many tech savvy people abandoned contact books decades ago. Contact books serve two needs - long term storage and quick reference to frequently used numbers. Computers have provided the long term storage, and various other facilities provided the quick reference, even before smart phones: human memory, print outs, sticky notes, pdas, basic cell phones.

In the 90s I knew people who'd set their browser homepage to a 'quick reference info' page on their server which included frequently needed numbers.

The only tech savvy people I've known to use contact books in the last twenty years seemed a bit eccentric to me.