I don't understand the problem, and the article doesn't really help. If I understand correctly, universities pay a fee to Elsevier to access papers. They also s

I don't understand the problem, and the article doesn't really help. If I understand correctly, universities pay a fee to Elsevier to access papers. They also submit their published papers to Elsevier. And (this is where I'm not sure anymore) they have to pay a fee to make their work freely accessible? Then why don't they just pay for the subscription, but don't submit anything? Or upload a freely accessible pre-print version like many people do?