You raise a good point, casting to rings on a smooth pond is another form of sight fishing; as is casting to tailing bonefish. When the ocean feeding coho salmon are tearing thru bait like silver lightning bolts or boiling the surface for candlefish, it's another form of sight fishing.
On Swiftshure Bank off British Columbia I could throw a fly in front of the wake of krill made by horse mackeral, using the pressure wave to "sight" in on coho. This remarkable phenomenon plays like this:
Pacific horse mackeral swim in a wedge to push the krill into a thick wave, gobbling as they go. Once the krill wave got thick enough, the speedier coho would zip thru the thickest part of the krill mass leaping over the bodies of the mackeral into the thick shrimp wave. You could almost sense when the wave would get thick enough for the coho to blast thru it, and once you saw a few breaking in front of the mackeral push wave you knew it was time to cast. And strip it like a madman or else you'll be tied up with a mackeral while the coho flash all around the boat!
It's not just the coho, I once landed a 20 pound king with a ball of krill the size of a softball in it's gut.
And who could forget the visual overload of a full-scale atlantic coastal blitz, the sound filling your head and the water black with the bodies of bass and blues pounding the bait against the shoreline at your feet! Sight fishing? All you can see is fish!
On another vein I enjoy reading the intense overall character of a glacial steelhead river just as much as I do casting to the stealthy forms within it's currents. In a sense, the river is a living thing and those who do well in steelheading "see" the life in the river. In this case, I think I enjoy fishing to visible steelhead less than the fishing of the visible river - because they are one and the same in steelhead flyfishing. When you fish to the river and hook a steelhead, you've caught them both.