You are correct as far as you go. And galvinized rigging is what is used on virtually all cargo ships, at considerable cost savings as well. Esthetics aside, you must consider that the standing rigging is attached to aluminum masts and spreaders. Use of galvinized raises the issue of isolating dissimilar metals to prevent galvanic action or electolysis between the two. That is actually quite a challenge and creates a perpetual maintenance problem. Given the fact that most boats are running around with their original rigging after more than a decade of use, the cost and slightly less strong stainless is considered reasonable.
If your point is; are we too stainless steel fixated, I'd certainly agree with it's use in ground tackle leading the way.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.