Two reasons, firstly if the engine has stopped and I am going to hit the ground anyhow it makes little difference to me whether that's in 4 minutes or six. Secondly, land flaps will make the descent angle steeper (thus reducing the risk of hitting a mast) and stall speed as low as it'll go, so my energy when I do finally hit something is as low as possible.
Thanks for taking the time to explain. I think I understand the effect of flaps. But you mentioned turning and I assumed that you would wish to stay airborn for as long as possible or until you decide its time to descend. My understanding and limited experience is that although landing flaps (i.e. much drag) would reduce your landing speed, they would also reduce the controlability of the aircraft. I think I would always maintain a configuration that would allow me to extend the glide for as long as possible until the point where I think I have a chance. Adding flap (esp with a PA28) is usually easy. Taking it off is invariably won't be. Maybe electric flaps pose problems with this particular scenario.