I don't have to believe in god to see that your body is an
incredible and naturally beautiful thing. Thinking you can improve it
with artistic whims and wounds communicates that you don't agree.
Saying that something is naturally beautiful and trying to "improve it" are not mutually exclusive.
That's true, but then you get into what counts as improvement. To my aesthetics there is almost nothing you can do to a healthy body to make it look better. If it's not a healthy body the best way to make it look better is to make it healthy.
I get similar feelings for two other things:
1) in regards to architectural elements which attempts to intimate materials. Vinyl (which is an amazing plastic) which pretends to be wood, (now ceramics that pretend to be wood), plastic that pretends to be metal, metal that pretends to be tile.
The function of the material is part of its beauty. This imitation tries to separate form from function. As if wood is intrinsically beautiful instead of it becoming a standard of beauty because it was such a useful material.
2) in regards to animal breeds which have clearly impaired functions, i.e. short legs, floppy ears, out of control hair, absurd over-muscle, etc... In these cases especially I see the ability of humans to create a standard of perfection that is profoundly divorced from function and when compared to the original species can only be classed a wretched mutilation.
Like I said the symbolism to me can be very different from what people who get tattoos or piercings think, but it's not as if there aren't plenty of options to make personal statements with clothing and hairstyle. They go beyond that and the reason why is very often, as Greyparrot speculated, because they feel like what they have and are isn't good enough. They look in the mirror and they can't face it, and I'm not just talking about surface appearance. They feel the need for permanent and/or damaging change because it makes it feel more like they are changing themself.
I think I must agree with Greyparrot because when I think of tattoos as they are used by say Polynesian traditions I don't feel any repulsion at all. The only difference is the perceived reason they're doing it.
Contrast this with the giant lip stretching ornaments of (those guys) in Africa (yea you know who I mean). I still think that's gross and in that case its because the harm and mutilation is present in an objective way that doesn't exist for well executed tattoos.