whois privacy being a service extra (sometimes included for free sometimes a paid extra which can expire and expose your data if you miss the email) where other TLD's (.uk springs to mind) already have the ability to withheld the personal details of domain registrants (private individuals have the ability to held their data, company registrations have their data shown) at the registry level and not having to use a 3rd party company.
I am an engineer working for a registrar and we've been told by at least one TLD that there is no difference. We used to "mask" the registrant email regardless of whether or not the customer had opted-in for proxy registration, and we were told this was not allowed by the TLD operator.
Well your still seen as the owner of the domain in the register’s eyes and not a proxy company which may help if you need to transfer the domain away from your registar for any unexpected reason.
Some TLD's don't allow proxy registrations.
whois privacy being a service extra (sometimes included for free sometimes a paid extra which can expire and expose your data if you miss the email) where other TLD's (.uk springs to mind) already have the ability to withheld the personal details of domain registrants (private individuals have the ability to held their data, company registrations have their data shown) at the registry level and not having to use a 3rd party company.