Probably to account for people who won’t store it properly, degradation of the packaging material, etc.
For example, if you store your blister pack of KI on a sunny shelf in your bathroom, UV rays eventually weaken the plastic packaging, cracks develop in the plastic letting in water vapor from your shower, and a stray mold space makes its way in as well and eventually you end up with mold growing on your pills. The KI itself may still be perfectly fine and able to do its job, but that mold might make you sick.
Probably to account for people who won’t store it properly, degradation of the packaging material, etc.
For example, if you store your blister pack of KI on a sunny shelf in your bathroom, UV rays eventually weaken the plastic packaging, cracks develop in the plastic letting in water vapor from your shower, and a stray mold space makes its way in as well and eventually you end up with mold growing on your pills. The KI itself may still be perfectly fine and able to do its job, but that mold might make you sick.