Evolution does not oblige us to change the oil any more than it obliges us to treat others as we would like to be treated. But if we wish our engines to remain in good health, or if we wish to remain respected members of our society, or if we value our own self-respect, we have to make the effort to change the oil or treat others with kindness, as the case may be. It's not something we need to be told by a cosmic Lawgiver.
Very many people are not interested in maintaining their car; it's too expensive or too much trouble. Likewise, people are not interested in maintaining moral or civil rules simply because it is good for them or for society. These people are better suited for a higher authority to provide that motivation.
