I can understand the covering of scars with tattoos, because most people and especially women have self-esteem issues about their looks, but I would prefer a scar over a tattoo because a scar is part of a person's circumstance, whereas a tattoo is a choice, a lot of times made without careful consideration.
It depends on the scar because all of them have a history.
For example, i have a scar i see more as a honor badge and lingering reminder to never lose sight of any weapon again.
In the early days of our shelter, before we confiscated (most) drugs and all weapons by default, one of the girls had a critical mental breakdown and tried to cut her wrists when i found her. She was far too deep in her own hell to listen or even become aware of my presence in the room despite talking to her. Trapped in her horrible flashbacks and dissociation i had no time for anything but acting fast, so i wanted to get a hold of her to force her back to reality and take her knive away. I managed to pull her back to reality, but not without taking the knive in the belly. However, i managed to calm her down enough for her to realize what happend, but she was too shocked by all the blood to call for help right away. I wasnt sure if i would wake up again or if thats the end when i slowly blacked out while i was still talking to calm her down. Well, obviously i was successful and survived it. The girl is also still alive and is one of the few who stays in touch.
Other scars are just reminders of fights, accidents, my surgery and animals in the past, all with an own story, some worth keeping in mind, most not worth to remember.
But many girls here have scars from all forms of abuse and other traumatic events in their lifes. Hiding them from distant lookers works, but they cant hide them from themselves and they are fully aware of it. These often get a tattoo makeover once they managed to come to terms with the past and are ready to move on.
I dont doubt there are girls out there who do it in vain for their self-esteem only, but i never met one of those. Or at least i never talked long enough with them to hear that reason personally.