With $1.0 billion you could invest $10K into 100,000 startups or $100K in 10,000 startups. Surely you could change the world, leave a legacy, and simultaneously generate a profit on that kind of investment, no?
$1.0 in "worth" does not mean $1B in cash. Also, the administration of 10,000 separate investment? How would you mentor the founders? Staff the boards? Would it be worth your time or your investment?
Why doesn't somebody do this?