It's useful for more complex situations than this. Let's say you have an object with a subsurf modifier, and you pass a reference to that modifier to some function:
mod = bpy.context.object.modifiers['Subsurf']
That function can now figure out the path of a property of the subdivision surface, like this:
print(mod.path_from_id('name')) # this outputs 'modifiers["Subsurf"].name'
Here is another practical example I just encountered. I want to create a driver for a specific property on the active sequencer strip. The driver needs to be defined on the scene itself, and I need to get the path for the property to drive:
se = C.scene.sequence_editor
'sequence_editor.sequences_all["2017-07-06T11-04-11+0200.webcam"].transform.offset_x', which is what is needed for the driver.