In a pizza restaurant I once placed my plate on the edge of the table while I gave plates to other diners. I misjudged the position and the plate ended face-down on the floor. I picked it up and asked a passing waiter "How clean is your floor?" He didn't answer. I was too hungry to wait for another pizza. No harm came of it, and it tasted fine.
I think sometimes we're over-obsessed with things. What harm could a little mud brought in on someone's boots really do? Even if they'd stepped in something the likelihood of them depositing anything really nasty on that bit of floor is fairly small. Of course, it wasn't during a norovirus epidemic, when things might be different.
We survived, and thrived as a species, for millions of years, eating the rotting carcasses of something else's kill, after they were done chewing on it first, before learning to hunt and kill for ourselves. I know I haven't dragged any steaks across a savanna littered with the dung of countless herds of various species, then let it rot for a few days, before eating it, but that was the main course for our ancient ancestors, and long before they had tamed fire to cook it. Maggot infested? Hey, that's just extra protein, along with all the other bugs they ate. Our immune systems are genetically programed to handle much worse than we're likely to encounter in the interior of our own homes, including the floors, even with pets around. Drop something on the floor? Brush off the dog hairs and eat it. Our immune system needs exercise too, if we want it to remain strong and healthy.