Why do you think privacy should be easier for domain owners? Shouldn't it instead be easy for a visitor to find out who owns the domain and is responsible (content, technical or legal) for a certain site?
Way too many weird people out there.
This is why I lie in my whois data, to the horror of the goody two-shoes on HN I'm sure.
The whois data is a great place to start a social engineering hack. The address or any past address is often used for identity.
Also your question may apply to the other end too. Shouldn't it be easy for an owner of the server to find out who is behind an IP address that is connecting to his server - and I mean easy access to his/her phone number, home address and a complete history of those, too?
It's easy to concot legal, technical and content reasons why this should be.
But perhaps there should be a possibility to remain anonymous (and the browser informing the user that this is the case).