because the chicken puts a 'bloom' on the egg that seals out any bacteria. Also, if you wash an egg you have to be careful that the water isn't too warm because that would open the pores in the shell and actually draw bacteria in.
I don't wash my eggs at all unless they are extremely poopy, then I just use a damp rag to wipe off the poopy spots
one of my customers won't take them if I've washed them, she'd rather see a little dirty spot than absolutely clean eggs
@katiedarling - yeah this guy started at my lower back, down across the cheek, down the outside of the leg, across the top of my foot, then back up the inside working his way back around to the back. Literally raising my leg off the table every time. The nerve damage in that leg is so bad he said he'd never seen one he had to hit with that much juice....