Wal-Mart's CEO makes $26M or so. The company has 1.2 million US employees. If the CEO cuts his pay to $2M, that gives every employee in the company an extra $20 per year. It might seem like a nice gesture and might make the news, but the extra $20 per year isn't going to make a difference for employees.
Now, that's just one example and there very well could be companies where the CEO salary could be cut enough to make a significant difference in the lives of employees, but you need to remember the context of the number of employees.