Why Do People Show Their Nasty Bare Feet?

My 58 year old BIL comes to my Christmas Eve party with moccasins and no socks on his feet. Why would he do that knowing that he was going to take his shoes off?  We are talking about Chicago, IL in December! Not only that, but then he sits in the chair with the ottoman so that everyone has a clear view of his nasty feet. 😖 No one wants to look at or smell your nasty feet. Do I actually have to make a list of rules for future parties like wear a pair of socks??? Embarrassing!