Some things you keep handy just in case something unexpected happens. What if multiple friends show up unexpectedly for a spontaneous pool party at your house? You don't want to break out the china, crystal, or silver. Just give them the tools to not look like a bunch of drunken Neanderthals squatting over the kill: Dixie cups, paper plates, napkins, and plastic flatware. Give them items that are useful, cheap, disposable, lightweight, and don't take up much room.
That is a simple analogy for a short term, simple survival kit.
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