How to interpret the term "Responsible"? What do we expect from him/her?

In MS Project, we assign one or more resources to a task.
Thus the PM remains in charge, and the resources report to him (by periodically updating how much work is done.)

But in ProjeQtor, we have an extra resource who is nominated as "responsible".
The help documentation does not explain how this concept works, or how it benefits over the direct management system.

1. What is the benefit of appointing a "responsible" person, if (s)he is not putting in any effort in that task?
In other words, if (s)he is not putting any effort in the task, how can (s)he expected to contribute?

2. ProjeQtor allows anyone to take up the responsibility for any task, independent of who is the resource assigned to that task.
It also imposes a condition that only the resources who are assigned to the project can take up this role.

BUT-
Would the resources not resent such unauthorized interference in their work, especially if a junior guy attempts to be "responsible"?

3. What motivates a person to volunteer to be "responsible" for a task?
Why would anyone take up an extra job unasked?

Is this "responsible" person a decision-maker for that task?
Or is it a supervisory job, which carries a little more respect/glory/power?
Or do we expect that the results and timings of each task should be validated independently by the "responsible" person?

4. ProjeQtor has a "Handled" flag, which only means that someone has accepted the mantle of being "responsible" for the job.
BUT setting the "handled" flag does NOT mean that work has started.
The resources assigned to the task can see in their TODAY screen, and decide independently when to do that work.
Then how is the "responsible" person work together with his/her "team" (resources assigned to his/her task)?

On the whole, is this a redundant idea?