Well, after cooking 100-200 pizzas a day directly on an oven floor, I'd imagine there would be lots of pieces of carbon. IDK why they didn't do it, just know they didn't. One restaurant used conveyor belt-type oven, so perhaps that is why they needed pans. The other two used brick-type ovens, but both of them used thin pans as well. I hear ya on the "not really unsanitary" thing due to the heat. But I imagine trying to keep one clean, what with spilled cheese, dough, veggies... not much fun, and not what a customer wants to see or smell when they come in. In a small restaurant, I can see it as not being a big deal. In one of the others I worked in, we did as many as a thousand pies a day. MUCH easier to clean metal pans than an oven...