Filing proposals takes a significant amount of time, expertise and resources. Some shareholder proposals are now advisory rather than binding. These are easier to get on the proxy and get passed, but they're largely ignored by management. Unfortunately, corporations often view shareholder proposals antagonistically, whether they come from individual shareholders or groups like Allied Owners or Lens. And the corporations usually respond legalistically.
Most companies view shareholder activism as a negative rather than a positive.
And just as CEOs resist interference from shareholders, so do boards. They have adopted staggered terms and eliminated cumulative voting. They have packed the boards with insiders, celebrities, and cronies. They have sought protection from state and federal governments. They have appropriated pension assets to protect themselves, they have rejected higher bids in favor of deals that benefit management, and they have paid greenmail to get rid of potential acquirers.