Answer
When an edit session is started on a line layer, the Construction Tools available in the Create Features dialog typically include Line, Rectangle, Circle, Ellipse, Freehand, and 'Create a line with Points'. Under some circumstances, however, only the Line construction tool is available.
The list of construction tools is filtered to show only the Line tool when working with line templates for layers with COGO attributes, layers participating in geometric networks, or turn feature classes in network datasets. This is because the other construction tools create closed ring shapes that are invalid geometries in those layer types.