Quick answer: Your dog sits on your feet to stay close, feel secure, and maintain physical contact — it's an affectionate behavior driven by pack instinct and attachment to you.
Your feet are accessible, stable, and warm. For a dog that wants to be near you, settling on your feet is the easiest way to maintain physical contact without competing for lap space. It's the canine equivalent of leaning against someone you're comfortable with.
Dogs that are mildly anxious in new environments or social situations often seek physical contact with their owner as a calming strategy. A dog that sits on your feet with strangers present or in unfamiliar places is using you as a security reference point — this is normal mild anxiety management.
Some dogs sit on their owner's feet as a social signal to other dogs — communicating closeness and familiarity. It's not aggressive but is territorial. More common in socially confident dogs in multi-dog households or social situations with unfamiliar dogs.
Sitting on feet is almost always affectionate or security-seeking. Only address it if accompanied by anxiety symptoms toward others or possessive behavior that creates tension.