ALWAYS because Hashem Said so. Present day morality, as we all know too well, is a relative concept. Depending on the society in which we live, it may be moral to euthanize babies and or the elderly or terminally ill. Pre-marital relations between the genders are no longer considered immoral by the secular world. Same gendered people are now permitted to go through the farce of a wedding ceremony. What was once considered seriously immoral is now acceptable societal behavior for many people.
ONLY the Torah is truly Moral. ONLY Hashem detemines what is moral and what is not. So we follow the Torah in the true spirit in which it is meant. That reminds us that how we deal with our fellow man in addition to how we observe the mitzvos that relate to Hashem Alone, is of the highest priority. if we do that, we will always be good people.