It’s coming from an agency with messaging that significantly factors in priorities given limited supply.
Of course kids and old people will be heavily preferenced in these guidelines. They always are. That doesn’t mean they should be valued the same way by individual citizens.
Anyone who cares enough, evaluated their own risks, and can afford to prep is obviously not starting from the same perspective of some generic recommendation going to hundreds of agencies across the country. You can argue risk levels but I doubt you could honestly dismiss the utility of personally supply for people in non-high risk groups.
Those at highest risk are infants and children, as well as pregnant and nursing females because of the potential for KI to suppress thyroid function in the developing fetus and the newborn.
Like why even believe that nuclear weapons are real or that potassium iodide is protective if you think that things are so far out of wack? The government is largely responsible for that knowledge.
Honestly, prioritising kids I get for sure, and pregnant women - but old people? Not so sure about their claim to a seat in the lifeboat, or a KI tablet in short supply.
Edit: Folks, the FDA page I link prioritizes children over people of fighting age. It lists lower doses for children because they are physically smaller but repeatedly states that they are at higher risk of harm.