IANAL but it is my understanding that if those tax reduction schemes are legal many companies are legally bound by their stock holders to exploit them, or else be found negligent in their duties.
That's not the case. There is no way a company's management could be sued for "gross negligence in tax planning".
If shareholders are unhappy about this issue, their recourse is the same one that's always available to them: elect a new Board of Directors and hire new management that will follow the board's guidance on tax evasion schemes.
What if the reason big companies avoid tax is that the shareholders ensure someone values fiscal results over supporting the country they earned the finance in is in the directors chair.
It's not a legal obligation though. Shareholders could choose to have corporations managed differently. That kind of "pro-tax" activist shareholders don't exist, but it's not inconceivable that large public funds (pensions etc.) could become such.
The problem isn’t Apple, the problem is the government can’t get its act together to pass tax reform.
The greatest example of board negligence in this industry (that I can think of) in recent years would be when Hewlett-Packard's board hired Léo Apotheker as CEO in 2010. The board members had never met the man and his career had been on a different continent, yet they didn't even interview him in person before giving him the job!
Apotheker spent $10.2 billion to buy a British company named Autonomy. Soon after he was fired. Only a year later, HP was forced to write down $8.8 billion of Autonomy's purchase price.
That enormous loss was directly the fault of HP's board for hiring such a terrible CEO and letting him do the terrible deal. But shareholders didn't have any recourse; the best they could do is vote on a new board.
Here is a list of hundreds of such open lawsuits:
HP actually paid $100 million in such a lawsuit for the Apotheker/Autonomy flop:
http://www.reuters.com/article/us-hp-classaction-pggm/hp-pay...
The 2010 Board of Directors who created and permitted the $8.8 billion loss paid nothing. They kept their compensation, and most stayed on the board.
https://www.delawarelitigation.com/2012/07/articles/chancery...
But there's nothing in the (US, at least) legal definition of a fiduciary that proscribes increasing share holder profits by any means necessary. That's simply a convenient myth spread to normalize cutthroat, profit-seeking behavior at all levels of business.