Smartwool wheel convection

Why do some animals obsessively lick the feet/hands of humans? - lick feet wrestl

We have three dogs and an obsessive licking the feet of us, and sometimes our society. Never lick your face, arms or anything, but if someone's shoes, goes directly into the feet.
One of our cats is so obsessed, but who lick their hands.
I know some people they lived with their animals or animals from people they know.

Why do some animals?