Pre-internet/cell phone nearly everyone had their name/phone number/address in phone books. Libraries had tons of phone books. And you could pay for the operator to find/connect you to people as well.
Contact info being private is a relatively recent concept.
Thread is discussing business contact details.
Also, it's not just about "a desire not be interrupted by people you didn't agree to be interrupted by", it's about not having the data in the first place, for any reason, including tracking of any sorts.