Why did england notgive the united states new orleans and florida when they gave up all land east of the misssippi river in the peace treaty?

During the end of the War of 1812 peace negotiations had begun in Europe but the word had not reached forces in Louisiana.  The British made an attack but were defeated by the Americans and New Orleans went under the control of the Americans. Later in peace negotiations the two sides agreed to return Spanish-Florida, which was controlled but the Americans at the time, back to the Spaniards.