Motivation for `just_points` in `VTKDataSetWriter`

What is the motivation for the just_points option in VTKDataSetWriter?

static void Write(std::ostream& out, const vtkm::cont::DataSet& dataSet, bool just_points = false)

The one unit test I found it exercised in gives this explanation:

  std::cout << "Force writer to output an explicit grid as points" << std::endl;
  vtkm::io::VTKDataSetWriter writer("Make3DExplicitDataSet0-no-grid.vtk");
  writer.WriteDataSet(tds.Make3DExplicitDataSet0(), true);

but I cannot understand why you would want to do that.

In addition, grepping through the user guide shows it is undocumented:

➜  vtk-m-user-guide git:(master) grep -nr 'just_points' .
➜  vtk-m-user-guide git:(master) echo $?
1