There is no legal requirement to maximize shareholder value. The very idea is an economic theory popularized by Friedman and his students.

It gained popularity in corporate governance since then but it’s not a legal requirement it’s a shareholder preference. But that preference is violated all the time.

People often cite a 1919 era case from Henry ford because it has a pithy statement but the court in that case explicitly upheld many of the decisions Ford made that violated the principle.

That is, there is no law or precedent that requires corporate officers to only consider shareholders.

It depends on your legal jurisdiction but it means COs need to act in the corporation's best interest and not their own. In some places, that requires them to take shareholders' interests into account (especially for mergers or takeovers) but also the employees, consumers or creditors. In the US and notably Delaware, courts generally value shareholder value over anything else.

Considering the vast majority of US corporations are incorporated in Delaware, I think it's accurate to say most US companies only aim to maximize shareholder value.