Of course the whole point for a firm like Jane Street is to make money. To make money means they are competing with someone and that someone could be a loser depending on the scenario.
My own opinion, most folks don’t like market makers or folks who work in financial markets are simply not well informed. The efficient allocation of capital is a valuable service to humans in a capitalist society. People often forget how wide spreads were in the past and that humans were swallowing that margin up with little competition. Now market making is highly competitive and because of it investors both small and large benefit from it.