Clean Soul
In between all the partying and evacuations, people would attend religious ceremonies. If you couldn't clean your body, it helped to at least clean your soul. Those who found solace in religion wouldn't even have to leave the premises. Of course, it probably got them away from the smell...
Roaming Rats
Rats were everywhere in medieval times. With a surplus of rotting food, the warmth between walls, open water sources, and plenty of places to hide, an old castle was a paradise for mice and rats. They came in large numbers and were a huge issue for the era...