Because the viewership is significantly larger for football. That's where the money comes from. Basketball programs like UNC can turn a profit and pay for itself because it's a blue blood and people buy expensive tickets and watch games. Not a lot of people are tuning in and buying tickets for Elon games.
Check out this page. Keep in mind UNC is an average football team in football and a blue blood in basketball. Football still wins out. And this doesn't even take into account the TV amounts.
Learn more about University of North Carolina at Chapel Hill sports programs, including how well they rank, how many student athletes the schools has, how much financial aid each student receives , and more.
www.collegefactual.com
ETA: After doing some quick searching, average viewership for football on ESPN networks was 2.1 million for football and 1.4 in basketball. That's only ESPN, so I would guess it's even larger if you add up all other networks. And I think the CFP draws significantly larger viewership than the basketball tournament.