The point being was there used to just be a big book with everyone in it, and now there isn't, and probably never could be again with how we all now feel about and regulate data privacy.
There are so many services now that have data scraped from various sources - many of them charge money, but they're readily available, even with increasing privacy laws.
> The point being was there used to just be a big book with everyone in it
There was never a big book with everyone in it. Maybe everyone in your city (more accurately, every household). But it was never even close to the scale of the internet. Linkedin has orders of magnitude more people than your phone book ever did.
Do you honestly think that you can't find out a heck of a lot more about people in general quite easily than you could in the white pages? (Which also required you to know the town/city where they lived.) For one thing, if you own a house, that's a matter of public record. Fortunately most of the deep search tools have gone behind paywalls but it's still trivial to find out a lot about someone especially if they have an uncommon name or you already know something about them.