They get the money they need. It doesn't stop at the coaches' level. Successful coaches at big time schools make more than the President of the United States or the President of their school. No, everyone gets a taste of the buck except the people who generate the bucks - the players. Slavery was abolished in the late 1800's and the minimum wage was just raised, but those changes apply to everyone but college students.
Athletic scholarships are renewable one-year deals.
I've known coaches who have chased kids off their teams so they could use that scholarship for another player that might help the coach keep his job. In addition, time demands on the athlete makes it nearly impossible to graduate within the 4 years of your scholarship. So, after helping generate millions for your school, it's adios and you're on your own. This is not only wrong, it's immoral. I'm not saying a scholarship and a college education aren't appropriate compensation.