Earlier quoted context omitted.
it's also why you shouldn't hold equity in your own company any longer than necessary (e.g., an apple employee shouldn't tie up the majority of their networth in apple stock).
My go-to example is always Enron, and the impact on employees whose retirement funds were in their own too-awesome-to-fail employer. Oh, sure, it's way worse because of the fraud-angle, but even if it had just been a more honest kind of mania, the arrangement was reckless and bad.
give somebody $1000 worth of shares in their company, and a lot of folks will hang on to them. but if you gave them $1000 cash to invest, they almost certainly would not choose to dump all of that money into their own company.