According to the Royal Academy of Arts there are three Art forms; Painting, Sculpture and Architecture. Recently they have introduced Photography as a fourth. Now we all know that Tattooing is an Art form; and the reason (or most probably the reason) why the R.A doesn't see it as such is that tattooing has not yet been introduced in the halls of the R.A. It has not been observed there; at all.
It's a good point because if tattooing IS an Art form (and we know that it is) then to diverse to it from another art form is quite within the rules of ART. The old school taboo rules that say you can't diversify into tattooing from another form is crap and soon to become extinct. These people that say this, are not Artists in my opinion.
The reason I think this is because Art is constantly evolving, it never stands still, it is malleable and ever changing. Creative Art is constantly coming up with new things. It never stops at the wall of one form either.
The other point I want to express here is; An individual either likes what they see or they don't. So when one produces a piece of Art, it is liked or it is not liked, simple. I suppose in the case of body art in the form of tattooing, a fully healed tattoo should be observed before any judgement is made. Like an Oil Painting it is not judged unless it has finished. If the piece needs more work, then it needs more work.
Moreover; a very important factor to a practitioner of any Art is that one develops ones own style in whatever form they choose to study. There is no set rule to say that one should 'conform' to the majority way of doing things. For another Artist to hinder or suppress the practice or learning of another is not the way the world of Art operates. I have observed many many times; and from highly competent individuals on the highest prongs of the ladder (R.A's even) that 'encouragement' and positive advice is best suited. Artists that hinder anothers progress are more often than not envious of the others abilities.