It was always possible to have a private unlisted number, though it typically cost a buck or two extra a month. My family and myself always chose that option, we didn’t want random people calling us.

And it's now sort of irrelevant with the increasing demise of landlines. And there's a ton of information that's public as a matter of public policy.

You could delist yourself from the phone book.

Most people don't want other people to be able to have that information about them unless they give it to them. I've been doxxed and it's not fun having that kind of information out there. There aren't many innocuous reasons people would be looking that up. Doxxing wouldn't even be a thing if it were harmless.