Luster, Gray Toning And Dipping: How Do They Relate And Does 1870 Matter?

I sort of think about dipping like steroids in baseball circa 2000: it's cheating but everybody does it to level the playing field. Unless it's done wrong, dipping appears more likely to enhance value (at least in decades past) than to diminish it.
Speaking of high grade (A.U. - M.S.) 19th century silver coins, in my relatively brief experience, most before 1870 seem to tone to a battleship gray color, usually with some, but not much luster. Although I have several high grade gray Morgans, most are bright and shiny, often with impressive luster. I also have a lustrous 1875s Twenty Cent Piece (ms63), a lustrous 1877s Trade dollar (ms63) , and a lustrous 1891 Seated quarter (ms63). I have looked at pictures of hundreds of other coins, and this seems to be the general rule, although I did find one dark toned, low luster type one Standing Liberty quarter with an ms66fh grade.
Am I seeing something that isn't there? If I am not, can someone explain why there seems to be an increase in untoned coins beginning in about 1870? I suspect it has something to do with dipping, which seems a little analogous to paint stripping. Dip a little, the toning comes off but much of the luster remains. Dip too much, and both the toning and the luster are completely stripped away.
So was there some change in dipping practices that has led to the gray/shiny dichotomy I have described? Are my later 19th century shiny coins (except for Morgans that spent 80 years in vaults unreleased) likely dipped?
What about later coins? Are bright shiny mint state Barber coins likely to be dipped, and as we move forward in time do we ever reach a point (Mercury Dime, Washington quarter?) where coins probably are not dipped? It probably doesn't make any difference in the market (no one would dip if people didn't like shiny coins) and ultimately maybe not in my buying decisions, as I only buy coins I find attractive and enjoy looking at, but I am curious.