If I’m a stock holder or potential buyer of stock and I read that the CEO is dumping billions of dollars of his own stock, I am going to think something bad is happening. Notifying the public in advance gives us more information to decide what we should do.
They don’t have to notify the public at all
There is nothing in the SEC laws that makes it necessary to disclose the use of Rule 10b5-1 to the public, but that doesn’t mean companies shouldn’t release the information anyway. Announcements of utilizing Rule 10b5-1 are useful in warding off public relations problems and helping investors understand the logistics behind certain insider trades.