A lot of reasons would arise: maybe they use tattoos as memorials. Tattoos can be designed for remembrance of a deceased loved one, of course, but they can also be designed for the purpose of keeping in mind other places or situations which a person does not wish to forget. To some they use this form of self-expression in a manner similar to what generations past used to do with t-shirts: to show the world what they wish to say. But most of them they get a tattoo simply because they want to have one. For many, simply liking artwork on one's skin is reason enough to visit a local tattoo studio, hand over a relatively-large sum of money, and have something etched into one's skin that is intended to remain there for the rest of one's life.
Speaking of tattoos, there is this chat room wherein tons of people from different places join the Tattoo Chat City and really enjoy themselves since it is absolutely for FREE.