There has been a lot of study on why people get tattoos. It's genuinely fascinating and worth learning about even if you have no interest in tattoos themselves.

It turns out that, regardless of history or culture, there is only a small set of motivations for getting them. I don't remember them all, or the nuances, but in general, the motivations tend to be to mark yourself as part of a group, to mark yourself as not part of a group, totem (commemorating an important event), artistic/aesthetic, and therapeutic (to help heal from trauma).