The market can only resolve based on public information, so it could only incentivize revealing information that is already destined to be imminently revealed. Furthermore, it doesn't incentivize sharing that information with enough lead time to actually take action based on that information; the opposite is actually true, insiders are incentivized to wait until just before the event to make their trade, meaning that the public gets no actionable information in practice. And that's assuming that you can distinguish an insider from someone lying for the sake of market manipulation.