When people started getting nosey and some entities started requiring personal information to acquire a domain name.
Some hosting companies and domain registrars offer the option, others don't.
There is/was a move on to eliminate hiding registration information. Not sure what happened to it. With recent events, that may get pushed again.
As with most other topics, I think there should be an in between line. Commercial and sites intended for widespread public use should not be allowed private domain registrations. Sites intended for personal use (like the one I have) could be exempted.