I think most of them are paid--they are called athletic scholarships, which are more generous than academic scholarships. The athletes get tutors and other perks that the average students do not get.
I have always contended that if an athlete did not earn a degree but landed a spot and a sx or seven-figure salary, he should be required to repay the scholarship to the school and let that money be used to provide academic scholarships to deserving students.
College sports are farm teams for major leagues. In my home town, LSU makes so much money from its athletic program, that it provides part of it to the school to help with overall maintenance.
Coaches are making millions per year. Athletes are attending three years or five years and often not getting a degree. Something is wrong with the system.