"It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest." Adam Smith's

"It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest." Adam Smith's insight helped launched the enterprise of modern economics because it turned out attention to what matters: results. Benevolence, like self-interest, is neither necessary nor sufficient to produce a social benefit. So you're right: the motivations of high-frequency traders are irrelevant, except insofar as we can change their behavior by changing the incentives they respond to.