When a shareholder dies, their shares pass to their family. The family may want cash rather than a stake in a company they do not run, and the surviving owners may not have the money to buy them out. Shareholder protection solves both problems.
Each shareholder's life is insured for the value of their shares, and a buy-sell agreement drawn up by your solicitor sets out how the shares change hands. The money can go to the surviving shareholders, who buy the shares, which is often known as co-director cover. Or it can go to the company, which buys the shares back. The family gets fair value in cash, and control stays where it should.