Karma is cause and effect. And of course, karma is much more subtle than, you kill someone, something bad happens to you. Sure, nothing bad might not happen to you now or this life, but karma is tied into reincarnation, and something will happen out of you in your next life that is not explained. I hope the last point also answers your thing about millions of people die from starvation. They might of not have done anything wrong in this life and seem to be innocent, but they might have done something their last life. They also might have done absolutely nothing wrong in their total existence, and be learning some lesson or something. It's really complicated, and I suggest you do a little research before you say such an ignorant blanket statement.
And your point on morality is also true, but humans like to have a reason to be good, it a religious, spiritual, or political reason. We like to explain things, and karma is one of the many ways we explain whats happening to us. How do you explain your goodness? ( I half assume you are a nice person )