It could be because of aesthetic preferences, to draw attention to a certain body part or be a cultural condition of which you conform to or rebel against. It’s a way to mark a certain age or status. A form of marking of a time in life is made and the piercing makes a statement of that this is the piercee´s body and his/hers alone. The owner of the piercing claims a symbolic control over how the body is modified. Other reasons worth mentioning are spiritual, sexual or even pure physiological. Some see this as a physical challenge where you test your pain tolerance and some might feel as if they get an improved sexual experience from a genital piercing, for instance. Whatever the reason might be, this is a timeless body modification which is semi-permanent; it lasts for as long as you want it to last.
When a piercing is removed and abandoned, it usually leaves very small traces of ever being there. Sometimes you cannot see anything at all and sometimes it retracts and form a scar as a little pore. With time it shrinks and how much it might be visible afterwards depends on how well it healed initially, placement and for how long you had it.