If someone wants to cover up their scars and wants to get tattoos, then they should do that. I don't care what other people do to their bodies; that's none of my business. Personally, I am not interested in getting a tattoo, so I wouldn't get one to cover up a scar.
Some people are very self-conscious about scars, and there are not many remedies out there that are good at providing results. If someone wants to get a tattoo to cover it, I think it is a great idea. It could potentially completely cover the scar, making it no longer visible, which is the goal of the person getting the tattoo. It takes care of the problem, which makes is a viable solution.
Many people have a scars for a variety of different reasons. Some may be worse than others, and some may be scars that a person would like to forget. There is also a good chance that a person's scars cause them to feel self-conscious. If covering these scars with tattoos makes a person feel better about themself, then I think it's a great idea.
If one likes and is willing to tattoo their bodies then using this method to cover up scars is a viable solution. The effects of a scar can have deep emotional impact for some and this is a respectable way to make someone feel better about themselves. A person should also be allowed to do whatever they want to their body.
Talk to your dermatologists or local tattoo artist before doing so but I 100% am for it. Tattoos can be so beautiful and magnificent. If your the type of person who likes tattoos I say go for it! Marks can be frustrating, my mother has one across her stomach from having children and had no problems. With the proper procedures and and treatment you are good to go.
Scars are meant to prevent people from bleeding. There will probably be blood under the scar, more so than if you didn't have the scar. Therefore, when they put the needles into you to make the tattoo(s), some of the blood might stay on the needles and go into the next person who uses it.