Why is the right hand preferred over the left for greetings, eating, and similar actions? And what prevents the use of the left hand for these purposes?

Allah Almighty has designated the right hand for noble actions such as eating, drinking, performing ablution (wudu'), and entering the mosque, while the left hand has been designated for less honorable actions such as entering the restroom and removing impurities. This is out of reverence and honor for the right hand, and in opposition to Satan, and because it entails exhibiting good manners with people. An exception to this is the inability to use the right hand, in which case there is no harm in using the left hand.