Why is Ethics is the only necessary knowledge?

Answer 1

...It's not. Ethics are importnant, but wisdom and true knowledge are also necessary to suceed in life. Tell whoever told you that ethics are the only necessary knowledge that they are wrong.
So when you're dying of startvation because you don't the knowledge of how to eat or make food, or dying of thirst because you don't have the knowledge of where to find water, you'll at least know that you didn't do anything wrong.

Answer 2

When we talk of ethics we talk about moral integrity and moral integrity as attested by the people is the true measure of man's greatness that is why ethics is considered to be the only necessary knowledge.