They aren't washing them. More commercial operations might brush them with a dry brush (to remove dirt and chicken poop), while others are just collecting them more immediately, but it's illegal in Europe to wash eggs -- which is required by law in America. Washing eggs removes the bloom, which coats them and protects the permable egg from infection. The trade-off is that European eggs should be washed just before use.

In America, we mandate that eggs are washed in a chemical bath. This diminishes the bloom and replaces it with a chemical wash.

Both mechanisms are ostensibly intended to prevent Salmonella, but I don't have data on which is more effective.