Financial market prices embody info that helps others to make decisions. For example, firms decide activity levels based in part on their stock prices. Thus traders who add info to such markets do a public service, even if they do this for a private profit.
I found this interesting, but don't see the follow-up on the alternative trading institutions/different market structures (at least here on substack).
Just in case you failed to post it for lack of engagement, I'm hereby indicating mine. 🙂