"I don't recall ever getting a strike on a snap swivel, not when there was a lure or bait on the end of the line for them to get instead."

That is interesting.

When fishing for trout in clear water I stopped using dropper rigs with swivels because I could see the fish hitting on the swivel a foot or two away from the lure. For that same reason, I stopped using (somewhat shiny) pinch-on lead weights and went to fly-fishing "mud" when I need to get a little more weight on my lure.

If a shiny swivel is no problem, I kind of wonder why fly fisherman use 8, 10, or 12 foot tippets?

Everybody has different experiences, I guess.