And yes, it is an art in and of itself. And it has nothing really to do with the process of putting a tattoo on skin. It goes back to the original meaning of the word *cartoon*, which just means a simplified image. Any drawing is a simplified image, a cartoon. And since a tattoo relies so much on getting a very few lines exactly right, it is one of the greatest challenges there is.
By comparison to drawing, photography is easy. Just about anyone can take a decent photo, even with their cell phones, these days. But getting that image to work as a tattoo involves simplifying it in a way that raster images (photography) simply can't do.
For most people, the greater the detail, the better the drawing. My point of view has mostly been the opposite. I compare a simple drawing to composing a simple poem, that is, boiling down to the essence. You can see this point of view in logo design, in Graphic Design, in cartoons, and yes, in tattoos.
Yes, a lot of flourishes and multiple colors can be added to any design, even a tattoo, but if the underlying structure is poorly done, it will always look wrong.