There is nothing locking teams into playing the NCAA tournament, which in 2019 made the NCAA around $800 million. That $800 is shared by the NCAA and schools/conferences that don't really drive any value.
This is going to end when there are 4 16 team conferences and those conferences will come together to host their own basketball tournament. Everything else is just filling airtime until it happens.
Add up the current SEC, Big 12, Big 10, ACC and Pac 12 schools and add ND and you have 63 schools.
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