Because Columbia has some of the best scientific and medical researchers in the world and they apply for competitive grants. That's how scientific and health research is funded in the United States, and we reap massive economic and health benefits from that research. For instance, Eric Kandel, who won a Nobel prize for discovering the biological basis of memory, is a Columbia faculty member. Columbia has a budget of $6.3 billion, so the income from its endowment can only fund a portion of operations. And even then, most endowment income can only be spent for a particular purpose specified by the donor and can't legally be redirected.