What is the reason for the prohibition of looking at the 'awrah (private parts) in the hadith: "A man must not look at the 'awrah of another man"?

Looking at 'awrah (private parts) is forbidden except between spouses, or out of necessity or a need that is equivalent to necessity, due to the Prophet's (peace be upon him) saying: "A man must not look at the 'awrah of another man, and a woman must not look at the 'awrah of another woman." The prohibition of looking at the 'awrah and the ruling on covering it stem from the fact that it offends both the observer and the observed, and it is a regression from innate nature and a loss of modesty. Furthermore, it incites lust and tempts one to indecency, and it diminishes human dignity. It remains for the Muslim to comply with Allah Almighty's command to lower the gaze and cover the 'awrah.