How to explain body modification to someone who is against it

I was watching tv with my parents and grandparents and my grandmother just says “Why do people get tattoos? Doesn’t it hurt?” I tried to explain that some places hurt more than others. She then said “Well if it hurts why do people do it?” And I only have piercing no tattoos so I tried to explain it the way someone explained it to me that it was an adrenaline rush and then she said it was “body mutilation” and that people in prison get tattoos and it’s prison culture.

So how do explain tattoos and body modifications to someone who is against them and uses that logic to justify why body modification is bad?