[1] http://www.dw.com/en/belgium-says-its-nuclear-plants-are-saf...
Because of the time required to evacuate people from the impacted areas, one of the objectives of a response plan would be to minimize radiation exposure due to contaminated food and water.
Providing iodine tablets before an accident is intended to minimize radioactive exposure due to contaminated food and water sources from the time the hazard is discovered to the time you are evacuated, and allows planners to apply those resources that would otherwise be spent distributing those supplies to helping evacuate more people, or responding to the incident.
And since that's normal and predictable, it should never happen except in cases of major force, like earthquakes and tsunamis. A government should be able to resolve the situation would letting the risk rise to this point.