The notion that a diplomatic agent should be immune from aggression of any kind in the execution of his or her duties is a very ancient concept. The heralds and ambassadors of times past were, by necessity, required to travel through unfriendly territories, and often to the enemy army itself.
Countries have a tendency to disagree with one another on certain items, and even go to war when these items are of great importance. Therefore, absolute protection of one’s diplomatic representatives is a fundamental requirement before meaningful negotiations can take place.
Exactly who is eligible for immunity is a question that has no concrete, immutable answer. The United States often grants immunity to those who are not entitled to it, while others, who are legally entitled to immunity, are omitted from the State Department’s “Blue Book”, the guide that lists ambassadors accredited to the US. However, when a question of immunity arises,
it is often found more expedient and productive to err on the side of generosity, rather than creating a potentially embarrassing incident.
Diplomatic Immunity - under International Law, the office and residence of diplomats are extended sovereign status, as such they are off limits to all governments and their agents - even in the host country. Free Diplomatic vehicle license plates (CC or CD). No travel or airport departure tax. Free upgrades on airlines, car rental, hotels and cruises.
It clearly does offer a great advantage to any person. A second passport means freedom from whatever forms of oppression -- fiscal or political -- you could be subjected to. A privacy tool and a means to reduce i.e.: taxation liabilities and to protect your assets, a second passport is of undeniable importance.
To the politically and economically oppressed or those unlucky enough to live in pariah nations, a second passport is a lifeline. Many countries are in the process of developing biometric properties for their passports in order to further confirm that the person presenting the passport is the legitimate holder. Restricting personal freedoms unnecessarily.
Diplomatic passports, however are issued by the countries for state employees or representatives who serve on long-term (resident) international assignments in other countries, usually two years in duration others have longer lasting validity.
Generally Governments do not want you to be freely shopping the planet for a passport or citizenship program based on features and benefits of a Diplomatic Passport.