I believe there is a strong argument for taking the prize, even if you don't need it, and not donating the prize, even if you would like to, so that people who are actually motivated by prizes do not feel they are obligated to waive or donate their prize. (A prime example of this is George Washington, one of the richest men in America at the time, who thought it was silly that he was getting a salary as president, and that it would be more public-minded of him to not collect his salary. He was convinced that if he did so, he might set a precedent, and this would prevent anyone but the independently wealthy from seeking the presidency.)