I don't mean to judge you, but...

Feet do generally carry a hundred or hundreds of pounds of pressure and, as such, are a odor-producing part of our bodies.

Wouldn't you want to show decency and respect to your fellow travellers by at least offering a sock and shoe's worth of a protective barrier between your odors and their noses?

You should be able to run around barefoot all you want in your own home but the aircraft isn't your own to do that.

I feel the same way about people who travel in tank tops and expose the rest of us to their armpits, by the way.