Because at some delay time the balance of risk moves from second-guessing random market movements - some of which are driven by insider trading and privileged knowledge - to second-guessing likely company performance in the real economy.

That point may not be a month, but I'm finding it hard to believe that enforced extended buy and hold, perhaps combined with strict volume limits, would have no effect at all on market dynamics.

Obvious manipulative plays can always be banned.

Of course no one likes the idea of not being able to sell instantly if the market tanks. But perhaps the market is much less likely to tank if no one is allowed to buy and sell instantly.

Once you eliminate predatory shorting and other games, real world conditions and disasters become the main driver of the markets. So you then have an incentive to minimise real world environmental risks too.