If I'm paying a lot for hatching eggs then I would expect them in the best condition. It's very muddy here and I don't have muddy eggs, so I guess I would expect the same. My theory is a few bales of straw are pretty cheap and would keep the chickens clean. One dollop of poop, I'm not worried about, covered in dirt and/or poo, and I wouldn't be happy. I agree that a broody would probably hatch them okay, but when we're shipping eggs, and hatching them in less than ideal conditions (no matter how hard we try), that you want to start out with the best. If nothing else I'd expect to be warned prior to purchase that you have muddy conditions and eggs may not be spotless.