> financial companies that hire a lot of smart people and make them do work that has little value to society

Would you rather I build a photo-sharing site? Chase tenure with esoteric publications?

Do you even know why I do HFT? I do it because it's intellectually stimulating and pays well, plus I work in a small firm of ten smart people and no corporate politics.

As for the value to society you don't believe I'm providing, my arbitraging makes it possible for products like ETFs to exist. Most retail investors would be best served with an index fund, and my work ultimately provides that service.