That's true. But, here's a little-known fact: unless you have a urinary tract infection, urine is sterile. So, it's much cleaner than your hands will ever be. Your hands are absolutely filthy, relatively speaking, and your guitar's neck gets coated with the oils, sweat, and whatever other spoonge happens to be along for the ride on your palms, fingers, and nails and holds the various bacteria, viruses and miscellaneous toxins in place that you come into constant contact with. Letting somebody play your guitar is almost like letting somebody use your toothbrush.