It is of course possible that an atheist can have a great sense of ethics.
This has to be based on Law however and Law evolved out of religion. Morality painfully evolved out of religions. (see evolution of law).
That important point aside, there is no need for a religious ethic if a person has a very strong legal ethic.
Sociologically this has now become a huge problem as the "cult of the individual" now expects individual ethics which are tailor made to fit each individual often outside the law.
Personal feelings of satisfaction and feeling good about oneself is still a "reward".
Many acts of charity are also a tax deduction! This is also a personal reward.
There are currently many unscrupulous atheists and "religious" people running businesses based on "charities" which give less than 5 cents a dollar to the needy while the businessman keeps the rest!
Once again the Law itself becomes the arbiter when such things occur.
Therefore it is morally wrong to assume a certain group has a monopoly on morality.