For me feet are a very intimate part of the body. Complete strangers will shake one another's hand, people don't have to be extremely close to hug one another, and some friends or in some cultures exchanging cheek kisses is a standard form of greeting. Touching another person's feet, however, that isn't normal social behavior anywhere. Massaging, or rubbing, or petting someone's feet is exclusively an intimate form of interaction between two people.
I also cum when a woman touches my feet, I get really horny then.