Back then they were home phones, they belonged to a household more than an individual. You had to be home to receive calls. Telemarketers arrived fairly late in it's existence. Robocallers were rare. You couldn't be spammed with text messages.

White pages worked because there were less bad actors.

You mean white pages :)

At one point as a kid we were getting a single FAT combo. Maybe that was a regional thing.

Sure, but the paid advertisements of the combination book were yellow and the opt-out listings were white; were they not?

Not necessarily. My first yellow pages as a kid were all one color.

(Small city)

People could opt out of that though.