When people in these cultures do body modification, it is an expression of something very human. Humans are the ones that have the capacity to do art. One of the earliest forms of art was modification of the human body.
In some cases this can be very abusive as in FGM or scarification rituals of young children, but in a lot of cases what we may view as ugly is meant to beautify the body in these cultures and is an expression of growing up or reaching certain life stages. Many of these traditions exist in societies without literacy. Someone from a jungle tribe might receive a tattoo signifying that they have reached manhood, or achieved a goal such as killing a member of a rival tribe, or became the chief of the clan. There are no records or documents so these markings are the equivalent of wearing a uniform or having a job contract. In a society where people have darker skin raised bumps from scarification can serve the same purpose as a tattoo in a lighter skinned culture.
What makes these practices particularly disgusting in Western culture is not only are they redundant (we have writing and other more efficient means of communication). They are out of place. A person with stretched out ears or lip in our society isn't communicating anything except that they want to be rebellious whereas in the originating society it was the opposite of rebellion.