Not sure if you are being facetious, but that's in fact the law. The board is a fiduciary of shareholder (investor) money. Is that a great idea for society? Not sure, until it changes we live in the world we live in.
And on the productivity point, that makes a good theoretical case but it is just not demonstrated by historical data. In the US, in the past 50 years, it even has a name (the pay-productivity gap or the wage gap). You can look at productivity vs wages since 1970 and see how they have not correlated. Further, you can go into income and wealth inquality growth over the same time (https://en.wikipedia.org/wiki/Income_inequality_in_the_Unite...) and see how the wealth generated by the productivity gains has been highly concentrated in the top 0.1% and 0.01% wealthiest. Some people will talk about real or nominal wages (adjustments with something called the Implicit Price Deflator) that show wages purchasing power increasing, but I think one can look at costs of home, college, and medical care and other critical things in social mobility that have increased in cost far exceeding inflation as complications to that idea.