It's because the SEC doesn't want them to do it. That is the whole reason for the short swing laws.
A short swing rule restricts officers and insiders of a company from making near-term profits. The rule mandates that if any inside shareholder holding more than 10% of outstanding shares or anyone that is an officer, or director, of a publicly traded company makes a profit on a transaction with respect to the company's stock during a given twelve month period, that shareholder, officer, or director, must pay the difference back to the company.
So if you had a large portion of your personal wealth tied up in one investment and you knew if you made profits in the near term you would have to give them back who do you know that would make that investment?