An exploit is a piece of software, a chunk of data, or a sequence of commands that takes advantage of a bug or vulnerability in order to cause unintended or unanticipated behavior to occur on computer software, hardware, or something electronic (usually computerized). Such behavior frequently includes things like gaining control of a computer system, allowing privilege escalation, or a denial-of-service attack.
1) Personal: The feeling of making an exploit or finding a vulnerability is incomparable. ?hat is the moment when you begin to feel really someone who is thinking outside of the box and begins to create his own "art"(what hacking really is).
2) Objectives: In many cases there is a need to build your own exploit and if you have this knowledge you are a step above ahead from the plethora of "professionals" with the many meaningless certifications.