H2G2 3:21 A towel it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value. You can wrap it around you for warmth, wet it for use in hand to hand combat, or even dry off if it’s still clean

 

…More importantly, a towel has immense psychological value. For some reason, if a nonhitchhiker discovers that a hitchhiker has his towel with him, he will assume that he is also in possession of a toothbrush, flask, map, ball of string…

 

… compass, wet-weather gear, space suit etc., etc. Furthermore, they will then happily lend the hitchhiker any of these or a dozen other items that the hitchhiker might accidentally have “lost.”…

 

What they will think is that any man who can hitch the length and breadth of the Galaxy, rough it, slum it, struggle against terrible odds, win through and still know where his towel is, is clearly a man to be reckoned with. Praised be Douglas Adams