Those things were printed at most once per year. Lots of information can change in a year. Online data can be as close to realtime as it gets. There's a large chasm of difference in MaBell's book and the internet. MaBell also would charge you to be unlisted, but you could provided fake names/info that would be printed in the book instead.

Addresses are still quasi-public information - they are published in all sorts of places, property transactions are published and available online. Someone's address is usually are easily found if you go looking.

Technology has made it far more dangerous. Swatting. Identity theft.

It wasn’t terribly practical for, say, a random person in Spain to harass, steal from, or cause the death of someone in the U.S. 20-30 years ago. Everything is global now.

Just because it happened in the past doesn't make it right.

Lots of very grave things were done in history that we now know to be mistakes.

Also, I always opted out in those days. I should still be able to do that today.

Yes, phone books are murder.