Yes, that is my rod and my box of flies: please return immediately!
I agree: most have the good sense to fish the appropriate rod. I am sometimes guilty, however, of leaving that good sense packed up with the rod tubes in the car. I often fish a two-hander purely for the intoxicating rhythm of the cast.
For me, the downfall of the two-handed rod is fishing a dead-drift dry fly (i.e. free-floating/non-waking). I like to position myself slightly below and about 30 feet from a visible salmon. A single-handed rod is more accurate at that distance and more stealthy.
If I can, I rig up two rods: a 9' for #8 wt. with a dry fly and a 12.5'-14' two-hander with a wet fly. I have yet to find one set-up that performs under all conditions with equanimity, but then I have never been shy about adding another rod to the quiver!