OYOYOY, at the end of the day, the reason you should do it is because Hashem gave us defining rules that HE knows will make us better human beings. Because He could not solely rely on our own innate sense of right and wrong (look at a baby’s or young child’s choices), He gave us a Torah to guide our actions, so that we choose to do the right thing. When you don’t know what’s right or wrong (back to euthanizing the elderly, or what the Nazis Y”Sh did to “defectives,”) you can rationalize away almost ANY wrong action and CONVINCE yourself that it is the right and moral thing to do. Ask that nurse known as The Angel of Death, if she did not believe herself to be a tzadeikes for killing all those terminally ill patients.
So the final answer to this question is, we should do it because Hashem commands us to, and He commands us only to do the morally correct thing.