Well, there's several reasons people get tattoos:
1) To cover up ugly scars
2) Tell a story of their life
3) Ancient tribes use them to identify with their ancestry and let others know in their tribe what kind of person they follow behind
4) Gang affilliates
5) Seems silly, but the pleasure of the pain and the beauty of having a piece of artwork for most people to admire (sometimes beauty is pain)
6) Because they're bored and want something to waste their money on (I know, that's silly too)
7) In remembrance of someone they lost and loved dearly
Just to name a few reasons. I know I got my tattoo to represent my family, myself, and my kids. Me and my husband are facinated with dragons, he has a dragon on his shoulder, our kids' names are down the back of his arms. The dragon is also a reminder that he is a kick boxer, the dragon is holding a ball with the Asian symbol for soldier ( he was in the army) and the dragon is in water, representing a tidalwave or tsunami, water is a powerful force of nature, like he is. He's also got a praying mantis on his chest, again for martial arts. As for myself, I have a dragon in the center of my back holding 2 roses. The dragon represents our family animal. The dragon represents me, a mythical creature, gentle but powerful, the protector of the roses, which represent my 2 kids.
I know that's a lot, and it still probably doesn't make sense to you, but from personal experience, that is why I got one. Plus, what most people will tell you, is that they just think tattoos are cool, some just get one to say they have one. Most of the time they don't have a story behind them, sometimes they do. The one thing I disagree with, is getting a girl/boyfriend's or spouse's name put on the body. Not a good idea. I love my husband, but I will never get his name put on my body, he said the same about me. Since they are permanent, choosing one that is meaningful to the person makes sense.