That depends. Say you've just parted ways with your aircraft a few seconds before a heat-seeker mated with it's tailpipe. Between you and any rescue is a hundred miles of bone-dry desert, 10,000 guys who'd love to add a dust-off chopper to their kill list before getting around to you, and half the enemy air force. What you've got to live on is what came with you in your seat-pan and any local wildlife you can kill. The local wildlife, BTW, is mostly scorpions and snakes with the occasional small rodent for variety. 1 quart of water will last you a day, maybe, if you're careful. The same space and weight can hold 4 days worth of those rations, 5 if you stretch it. Which would you rather have?

These rations aren't for regular use (or at least, not when prepared that particular way). They're for use when the alternative is broiled rat or as much sand as you can chew.