It's hard for investors to get Management in line of the needs of the investors, they mostly work for their own needs, take a look at the big bonuses and raises they constantly give themselves. Often even after a terrible year.

In big corporations there are so many investors that they are hardly organized. And even if they are it's a difficult problem to incentivize a manager correctly. It's a topic with a lot economical scientific research. In theoretical terms it's called the principle-agent problem.