Because that makes iodine an intervention easier to market to feminists and anyone with feminist leanings, and increases in female intelligence may have positive effects on particularly benighted and distasteful countries like Afghanistan or Pakistan.
This is interesting, I wonder if there's anything to it: International variation in IQ – the role of parasites (paper) by Christopher Hassall of U. Carleton.
It strikes me as the sort of thing that could be as big an issue as lead in the environment. Raise the sanity waterline: improve health!