Because anyone who knows anything about the history knows that Argentina's 'claim' comes from a disputed agreement between France and Spain that not only happened before Argentina existed but also did not include Great Britain. And that is ignoring their little war that they lost.
Code:
1493: Pope Alexander VI issues a Papal bull, the Inter caetera, that divides the New World between Spain and Portugal.
1504: Binot Paulmier de Gonneville (France) sights islands that may have been the Falklands.
1592: John Davis (England), member of the second English expedition of Cavendish, shelters among islands that may have been the Falklands. The Falklands motto Desire the right is in part based on Davis' ship Desire.
1604: Treaty of London between Spain and England. Terms largely favourable to Spain set aside "what had been able to acquire previously to its signature".
1670: Treaty of Madrid. Spain recognised English possessions in the Caribbean Sea, and each country agreed to refrain from trading in the other's territory.
1690: John Strong (England) landed, and named the sound and eventually the entire island group after Viscount Falkland, Admiralty Commissioner.
1713: Treaty of Utrecht between Spain, France, and Great Britain. Spain later claims this granted Spain sovereignty over the islands based on the Treaty of Tordesillas, a claim rejected by Great Britain.
1764: Louis de Bougainville (France) founded a naval base at Port Louis, East Falkland.
1765: Ignorant of de Bougainville's presence, John Byron (Great Britain) claims Saunders Island and other islands for Britain. Britain builds a settlement on Saunders Island the following year.
1766: France and Spain reach agreement: French forces are to leave, and Spain agrees to pay for the installations built by de Bougainville.
1769: British and Spanish ships encounter one another whilst surveying the island. Each accuse the other of having no lawful reason for being in the islands.
1770: Falkland Crisis: Five Spanish ships arrive at Port Egmont with over 1400 troops under the command of General Madariaga. The British are forced to abandon Port Egmont and threaten war.
1771: That dispute was settled, with Spain retaining Puerto Soledad and Great Britain Port Egmont. Spain returns all goods and chattels seized and makes restitution. The Spanish later claim a secret agreement was reached whereby the British would leave the island, this is denied by the British and no documentary proof of the agreement has ever been produced.
1774: The British decide to evacuate many overseas settlements due to the economic pressures of the American War of Independence. The British garrison departs the islands but leaves behind a plaque asserting British dominion.
1780: Sealers occupying Port Egmont are evicted when it is destroyed by the Spanish to prevent the British from returning.
1790: Nootka Convention. Britain conceded Spanish sovereignty over all Spain's traditional territories in the Americas. Whether or not the islands were included is disputed.
1806: Spain recalls Governor Juan Crisostomo Martinez from the islands but leaves behind a plaque re-asserting Spanish dominion.
1811: The Spanish evacuate Puerto Soledad, the islands become the domain of sealers and whalers.
1816: The United Provinces of the Río de la Plata, later called Argentina, claimed independence from Spain.
1820: After an 8-month voyage, and with the ship in a poor state, the Argentine frigate, Heroína, puts into the islands in October. On 6 November Captain Jewett raises the flag and claims the islands for the United Provinces of the River Plate.
1825: The United Kingdom recognised Argentina's independence from Spain.
1828: Vernet's settlement established.
1829: Buenos Aires issues decree setting up "Political and Military command of the Malvinas". Britain protests.
1832: Argentina sends a garrison commanded by Major Esteban Mestivier. Mestivier is murdered following a mutiny.
1833: Britain re-establishes control of the islands.
1841: General Rosas offers to relinquish any claim to sovereignty over the Falkland Islands in return for the relief of the Argentine debt to City of London interests. The British decline the offer.
1843: Work begins on the new town of Port Stanley
1850: Britain and Argentina sign the “Convention between Great Britain and the Argentine Confederation, for the Settlement of existing Differences and the re-establishment of Friendship”. Several historians (Argentine, British and Latin American) consider this has a negative impact upon Argentina's modern sovereignty claim.
1881: The Falkland Islands become financially independent.
1884: Argentina requests that the sovereignty dispute be submitted to independent arbitration, Britain refuses. The first mention of the Falkland Islands by Argentina for 34 years.
1945: Formation of the United Nations, Argentina states its claim to the islands in its opening address.
1946: Britain includes the Falkland Islands among the non-autonomous territories subject to its administration, under Chapter XI of the UN charter.[2]
1947: Britain first offers to take the sovereignty dispute over the Dependencies to the ICJ. Argentina does not accept.
1948: Britain again offers to take the sovereignty dispute over the Dependencies to the ICJ. Argentina declines.
1955: Britain unilaterally refers the sovereignty dispute over the Dependencies to the ICJ. Argentina indicates that it will not accept any judgement.
1976: RRS Shackleton is fired upon by the Argentine destroyer ARA Almirante Storni during Lord Shackleton's mission. Argentina establishes a military base on Southern Thule. Britain protests but seeks a diplomatic solution.
1980: Nicholas Ridley proposes leaseback solution, it is rejected by the islanders.
1982: Various tensions, but mainly the desire of the Argentine military junta to distract attention from domestic economic and political ills, led to an Argentine invasion. The islands were later retaken by the UK. (See Falklands War.) In November, the United Nations General Assembly called on the UK and Argentina to resume sovereignty negotiations, but the UK refuses to discuss sovereignty unless it has the consent of the Islanders. An updated Shackleton report on the economic prospects for the islands is published following the conflict.
1994: Argentina enshrines its claim to the Falkland Islands in its constitution.
2013: Referendum held in March, overseen by international observers. Falkland Islanders voted to determine their future, 99.8% of the electorate voted YES to maintaining current political status as a British Overseas Territory.