I've thought about this plenty of times, my conclusion is usually the same:
I really don't see the use of piercings, they don't add any 'beauty' to my eyes, rather, they take away lots of it. They're also very unpractical, can cause infections if made wrong, can be dangerous if they get stuck with an object. Can you imagine the pain of having one of them pulled out of your skin because it got in the wrong place, like some cloth?
As for tattoos, it's almost the same. They don't add anything super duper, and the ink filters through the skin and those microparticles eventually reach your blood. You wouldn't want having ink in your blood, eh? I know, it's not like hundreds of people die from ink intoxication every year I guess, but it still adds up to the list of factors that can end up harming your body.