In the early days, especially for individuals, some registrars required ID proofs (ID card, passport, etc.) to register a domain, and put you full information into the records. There was no way to put fake data there (unless using fake documents as well).
That's because there were some stringent rules about domains requests and domain names, especially if one wasn't a registered legal entity - many of them relaxed later.
Once people had no issue to have their name, address and phone number published in phone records, now that robocallers, spammers and other various crazy people multiplied through the internet it became just a risk.
I didn't bother much twenty years ago about having my data published in the whois records, but now I requested to hide them - and after GDPR it was done for free.
