Are you asking why you need a profit? Really?
So that you can pay your bills and go out for pizza once in a while.
It is desirable because all the enterprises in the world run solely on profit and there is no other reason for this besides this other than profit. No profit then no motive and hence no enterprise or business.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them