Many people decide to take a course which they feel that a piercing is not enough and decided to create something unconventional and not everyone dares to do. The example is in the following picture which shows a "corset" done with multiple piercings in the back of the girl shown in the picture.
There are people who want to go a little further in terms of creativity referred to as is the case of the person who decides to inject ink (not any kind of ink) in the white of the eye which also changes the color to be permanent (as I have understood). Look at the picture below to be able to see how it was done.
Everyone has their tastes and way of expressing. To each its own.