The main reason people choose to get any tattoo is that they like how it looks on them. In the case where a person has a scar that reminds them of something unpleasant, they have an extra reason to hide it. Something to keep in mind is that scar tattoos are generally more painful than regular tattoos since the needle paints over scar tissue. And while there are serious considerations you should think about, there are some people who get over their fear and trust their tattoo artists.