Blankets are multipurpose items.  One, it covers the stuff in your car to make it a wee bit less attractive to a thief.   If you get a reflective blanket, you can attempt to shield yourself from the sun or wrap up someone who is injured.  It can become an emergency tent or a flat pillow.  If you end up in a shelter, unexpectedly, you can sleep on your blanket.  Most of the last minute "shelter of last resorts" do not have blankets - they are safe places to be, but not comfortable!  Remember they didn't have time to prepare so if you have a cot, you'll be lucky!