Shares of the company they work for would incentivize them to care about the company.
Shares of other public companies means no skin in the game. A day trader cash out whenever they want and wipe their hands clean of any adverse effects made by the company in the name of growth.
It's true, which is why I think it's good to make shares part of the compensation.
That being said, employees already have skin in the game because they want their company to survive so they keep their job. When a company goes belly up, employees with shares are worse off than those that bought shares in other companies instead.
