"Lastly, from a more theoretical point of view, insiders provide information to the market by means of their transactions. Thanks to them, this information reaches the market faster than it would without their involvement, which in turn accelerates the approach of stock prices to the real value of the stock. This process has been explained by Rothbard in his analysis of the social role of speculators.1Moreover, the mere fact that an insider wishes to sell or to buy provides information on the stock value."
https://mises.org/library/free-market-approach-insider-trading