You are correct. In nature there is only iodide. So this supports your theory that Iodine is not needed.
However we are also talking about Iodine being used as a medicine to cure serious disease. And in this application, the Iodine doctors have been promoting Lugols and the Lugols formula and have been extremely successful for 125 years.
Are the doctors wrong? Which iodine do you say should be used in case of Deficiency Diseases?