This is exactly the right question. If quant firms make the world a better place by tightening spreads - a common justification - then wouldn't we get an even better place if everyone knew about these strategies?
A counterargument here is the effects on internal transparency. If a quant firm knows its employees can leave and join a competitor tomorrow, they will be less forthcoming with IP. The lack of openness could lead to lower productivity within the firm, as work gets duplicated and teams can't share their insights with each other.
As long as we're throwing around generalized hypotheses, a company that shared internal IP freely, and also compensated people such that they didn't leave, would gain a lasting competitive advantage.
