To be honest, I wouldn't recommend removing the data from these privacy tables is because the system only uses this setting "Enable Privacy" to determine that whether need to check the user privacy before rendering the item.

In other words, if this setting is disabled then the system can retrieve the data will be fast if compare when you enable the privacy setting is because from the SQL query wise, it doesn't need to check for the user privacy when executing the SQL query on the server.

Just for your information, even you disable the "Enable Privacy" setting, it will still generate the user custom field or other item data into these tables is because the system also needs to handle this what if the site owner decides to re-enabled back privacy in one day.