They can’t really tell the difference between “front hands” and “back hands”. Your “back hands” (feet) have a stronger scent of you on them, and also, due to your height and bipedal nature, your “back hands” are the part they see most and closest.

I lived with family and they got a puppy, he would sleep with his head inside my stinky leather boots and he loved it.

My cat used to also sleep with my shoes but at some point he stopped doing it.

Animals just love feet smell.