Is it really that difficult to have enough supplies just for 72 hours? You don't even need any food for that short of a time, and you only really would need, what, 2 liters per person? Personally I drink a lot more than 1 liter of water per day, but in a crisis situation you're gonna ration it
The goal of such recommendations is not to ensure people can survive 72 hours without access to additional supplies, but to ensure that the society as a whole can function at such a situation - that requires a lot more than just a drop of water and barely enough calories to stay alive. If the enemy can collapse your society just by destroying a couple of power plants and water treatment facilities, you've already lost the war. Or climate change, or blizzard or what ever it is you are facing.
That being said, I do agree that the food you store doesn't need to be anything special or tasty - just something to keep you working your job and taking care of those that depend on you.