being an artist truly means putting yourself out there. it is putting your most vulnerable self for everyone to see, and to even comment on. even though art is supposed to be "a form of expression" people are very judgmental about it. some believe a single dot on the canvas is absolute genius, but an artist who poured their blood, sweat and tears into a masterpiece (whether it be a still-life, an outdoor scene, etc) is too simple and anyone can do it.
but being an artist, a person is able to hide behind their work, but as a tattooer, the person is front and center. if they mess up, they mess up on someone else's skin and that is permanent. yes tattoos can be removed or covered, but that does not mean they are completely gone.
as a tattoo artist, it is very nerve wracking because if the tattooer messes up there can be a law-suit. yes there is the argument that it is creative expression and that the artist meant to make the mistake or meant for the tattoo to look like that, but no one wants to be brought to court.
if the artwork is on a canvas, then no one can really do anything because a canvas can be painted over it just may take a lot of paint.