Morality - good for what?

It is supposed to be a given. You are supposed to believe in morality. You are supposed to be a "good, moral person." You are not supposed to ask, "why?"
But before anyone can begin to answer why, there needs to be some agreement on what morality is. It is here the problems begin.
Every religion has its basics and its exceptions to the basics. Murder is universally regarded as bad moral behavior but the problem here is in the definition of murder. Exceptions include war, state executions and self defense to name but a few.
"Do unto others as you would have others do unto you" seems to be a safe standard of morality but is often violated, not only by individuals but also by business and governments. You are considered a fool if you don't charge as much as possible and pay as little as possible in business. Many governments consider preemptive strikes wrong if done to them but okay if they do it.
Sex! Here we are consistently inconsistent. It is a minefield of yes-yes and no-no. So much variation from one religion to another and one culture to another that to come up with one standard is probably impossible at this point in time.
Considering the variety of interpretations on what morality consists of, it may seem pointless to ask what morality is good for. But if you think about it, I think there is an answer.
What I suggest is this. Morality, however the particulars might be defined, is simply a way for a society to function with a minimum of conflict. Generally speaking, instinctively we know we should do unto others as we would have them do unto us. The problem comes when the survival instinct overrides all other instincts and we end up doing unto others before they can do unto us. What we fail to remember when we do this is we lose all rights to expect the other person not to do the same. It comes down to who is the bigger bully, who shoots first and who has the better lawyer. And we end up with the mess we all complain about, certain we are the moral person while the other is morally depraved.
In an odd twist of fate, we use our version of morality to commit immoral acts upon those with a different set of morality. People of one faith feel justified in oppressing and even killing people of another faith.
Meanwhile, in our heart of hearts, we know we don't want to be killed, raped or robbed and realize, in our heart of hearts, neither does the other person want to be killed, raped or robbed?
Simple? Yes, if only we could control our fears and thus keep self preservation in check.