Considering one's nearly $50B endowment, why isn't tuition free at the ivy league universities?

This isn't a socialism question where some people think everything should be free. But if a university has tens of billions of dollars in their endowment fund and it's making even a modest 5% interest, that should be more than enough to cover salaries, utilities, building maintenance, etc. What's the point of an endowment fund if it's not benefitting students?

Considering one's nearly $50B endowment, why isn't tuition free at the ivy league universities?
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