The cost of food is very predictable and pretty flexible. Anyone who needs to can eat well on <$100/week as long as they have access to a reasonably-priced grocery store and facilities to cook and store food. (Also, note that even our barebones welfare state includes foodstamps.)

On the other hand, medical costs can vary wildly and randomly. A perfectly healthy person who's been following health best practices might suddenly develop a serious condition that is treatable, but only with five to six figures of treatment.