I guess when I speak it's from a SPS point of view. With a LPS tank, or soft corals, I might be less inclined to change as much for corals, although the fish would still have to be considered. I guess my philosophy is to keep it as close to natural as I can, given the small space. I just know that when I'm swimming down in the tropics, I don't mind getting a mouthful of water, but I sure wouldn't want tank water touching my lips
I've pulled fish out of the ocean for my selfish enjoyment, I feel the least I can do is keep the water as clean as possible.
Now sure, it can be done. Steve will pop in here shortly and tell us how he ran his tank for over a year without changing water, and his corals had some color. But....is this optimal for all the creatures in the water? Or is it sufficient to meet our particular requirements (color, growth, whatever it is we each want from the tank). I would guess the later. A tank can and often will be successful, within the measurements of our individual requirements for success, without water changes. Will it get worse by changing water? I don't think it would. Would the fish be healthier/happier with water changes? I suspect so..