Here's one way to look at it: When you give your money to Gates you generally know what you're going to get - stamping up diseases, immunisation and lots of other great stuff.
When you give your money to Musk, you don't. It's much less clear. You don't know what problems he's going to tackle. You don't know how he's going to tackle them. And you don't know if he'll succeed.
1. Giving your money to Bill is like investing in a tried-and-tested branch of science or technology with measurable possible outcomes.
2. Giving your money to Elon is like investing in an absolutely cutting-edge branch of science. At the absolute bleeding-edge. Maybe even beyond the bleeding-edge.
Both are important. Here's a story to show you why.
One day back in the 1930s, before the war, all the academics in the USA found an unusual survey in their pigeonholes. It asked them to rank all the various academic departments in the USA by importance. Most important at the top. Least important at the bottom. They were asked to use their intuitions - what did they feel were the most and least relevant to the future of humanity.
After the academics filled in these surveys, their responses were gathered up and collated into a league table with the 'most important' disciplines at the top, and the least at the bottom. What was at the top? All the usual suspects like branches of physics, chemistry and biology.
What was at the bottom? Right at the bottom was Medieval History. The very least important academic subject. So far, so unexpected. But second to bottom was Nuclear Physics. Before the war it was considered a useless, hypo-theoretical branch of science only studied by nuts and eccentrics.
Of course, not much longer later the US dropped 2 bombs on Japan ending the nuclear war.
If we'd only funnelled our money in those things with obvious tangible, well-defined outputs, we'd have shut down our nuclear physics departments and the world would have been a very different place.
What I'm saying is that investing in long-sighted, ill-defined, radical, impractical projects is not only valuable but essential.
Dropping money to people like Bill is important. But so is dropping money to Elon.
One of them ensures that we continue to make sustainable progress - that we continue down the road that we're already walking. The other ensures that we have the opportunity to find new roads, new paths and new routes.