I have heard the same thing a few times, but I know personally that I would not (I could never live with that much much of an idea of permanence) and mostly that was by people who had no tattoos themselves or even began to understand the tattoo process. Its like telling a person who can draw skateboard that they can easily snowboard, while they may be similar in mechanics they are different to handle and require their own set of skills. There is a respect that needles and skin are NOT like pencil and paper. I have seen my fair share of horrid tattoos.
If you love drawing and people want your work that is great! But it is very rare to find great talent amongst the pleasure group. Cause if you love doing something and you're good enough at it, why do it for free? Those that want it to be a career HAVE to be great. So they work very hard to perfect their work. So by nature their work is better. Just a fact of life, I'm going to always choose the farrier who does it for a living over the person who only does their own horses and might offer it to me cheaper. Its just a level of professionalism.
I've done a lot of nice work for free, including wood burning, I did it in high school and every now and again when i'm at home. I have a friend who made it a business, and he does it in his spare time. I have great potential, my dad tells me all the time I need to go to art school, but in my area art isn't in high demand, so I chose not to. Plus if I have mental block how is that going to help my career. I'm always bettering my skill, working and improving. Where my work is heading now is airbrushing, I can do it on paper and on a car. I like to work with charcoal, I can't paint with a paint brush to save my life, and I prefer pencil sketching. I'm not out there trying to be great, i'm just willing to share my art with others to maybe help inspire them to do something great with their own talents. I have another friend who is way better than I, and he works in a lumber yard, and won't go and become a professional. We're out there, some of us just don't choose to be in the spotlight. Plus I couldn't afford to go to art school anyway, its too far of a drive and expensive.
I got my artistic talent from my dad, he's a mechanic/body man and has his own garage. He sketches paint ideas for cars in his spare time, or does it just for fun. Airbrushing is his true talent, and he asks me to help on occasion with difficult designs, or animals. I have great respect for professional artists, I love their work, and i'll use it as a reference to help with my own skill.