Why does one have the Ego?

Following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

Question: Sir, why do I have ego?

Acharya Prashant: Do not ask, “Why does the will-o-wisp, or the ego, or your personal center still exist?” If you ask, “Why does it exist?,” the answer is — your birth.

It exists because, you do.