Working a prop trading firm is nowhere near "making rich people richer via gambling in the financial markets".
Furthermore, the majority of software/engineering jobs out there are not doing "something more beneficial to society". How many companies are really just ad-driven, marketing-driven.
Yes, it would be nice if the entire world could focus on "something like curing cancer", but other things need to get done. And the majority of people have bills to pay.
I am very similar to the OP, except I bailed halfway through the PhD, because I realized that, in academia, I will work 80 hours a week for $40k, or I can go into finance and work half that and make multiples more.
I can now donate/spend my money to causes like "curing cancer" or "making art" and let somebody who really wants to devote their life to that craft do so.
Some people think research or science is the only path to a better society but in all honesty it may just take paying people in a poor country to plant trees.
That said, research is seriously underfunded.
"When I was a little boy, I used to pray every night for a new bicycle. Then I realised, the Lord, in his wisdom, doesn't work that way. So I just stole one and asked Him to forgive me."
Sometimes to get what you want you have to sell out or otherwise find an unorthodox means to your desired end state.
The list is extremely partial. I'd be much happier seeing other contributions to it than sniping about significance.
Yet, every time finance work is mentioned, someone brings up "I can't believe you work in finance instead of curing cancer."
Guess what? I don't want to work on curing cancer. I used to. I went to school for biomedical engineering and wanted to work on big problems. I realized I would rather do as little work as possible (but still be challenged), and spend time with my family and friends. And I'll happily give money to people to cure this problems.
And those big problems that I wanted to work on before? Well, I'm sure there's somebody that really cares about that. The best way I can help is using my time in ways that I enjoy, and giving my money to those who will actually enjoy finding that cure.
A friend of mine almost died from some disease when she was in her teens. She survived, and is now a researcher for that specific field. She has a personal interest in that research, even if it means she might have to sacrifice other things. And she was also the one who convinced me to bail from the PhD program. She said "if you can imagine yourself doing anything else, do something else."
That's when I realized academic research is long, painful work, but you have to be excited for it. If I'm not excited, I should do something else, and then give money or help increase funding to make it less painful for those who still want to be there.
tl;dr - Go short on PhD salaries!
I was simply addressing the absurdity that our smartest minds are incentivized to go into finance rather than work on the most difficult and important problems in the world. The modern day Albert Einstein is probably working at a hedge fund. If we allocated humanity's resources differently, then we could be so much more technologically advanced.
This is a big problem in itself.