Ever work with an employee that you thought should be fired but seemed "untouchable"? This article outlines at least 10 Reasons Bad Employees Don't Get Fired. I've personally seen most of these reasons in action over the course of my career.
So what is the lesson?
Managers cannot address every single problem at once. Their primary focus is always to grow the business in order to project the jobs of the majority. They will deal with problem employees as they have the impetus and time. Therefore there have ALWAYS been problem employees in every workplace, and there always will be in the future. If you can understand this, then it is easier to not let it get to you when someone else doesn't receive their "just desserts" for underperforming and creating chaos for others.
Remember that you never know the entire story. The key is to focus on your own work. What are the goals of your Manager/Department? If you can work to advance the business, and put in place the building blocks of your own great career, you will see great things happen!