If we could think of software development as an economy, team members would be businesses and project manager the state.
Let me explain the analogy.
1. Businesses demand laissez faire - they don't want state intervention in the running of the economy. Much the same as software development teams.
2. Over the past years, we have seen how businesses can run the system aground, left to themselves. Its not that businesses like to run systems aground. Its just that businesses tend to focus much more on their profits than the welfare of the system. Same with the software development teams.
3. Enter macroeconomics. There are times when the state has to intervene. This could be reactive, when faced with a recession. Or preventive. In either case, it is necessary that the state monitors the economy and businesses and intervenes in a timely and appropriate manner not to suppress enterprise (which is key to a free market economy), but to foster economic stability and growth. Can't state the responsibility of project managers better than that.
4. As somebody said - state should not do more (or less) of what businesses are supposed to do but do what businesses don't do. States aren't expected to run businesses. States, however, are expected to understand the overall economy. Project managers don't need to write narratives or code. They should, however, have a sound understanding of the overall software development eco-system.
Note - I am not criticizing the software development teams as much as enunciating the need for continuous monitoring and timely and appropriate intervention of the project managers.