That's a good question, but a very tough one to answer. There are several factors to consider.
How common was it with the cattle present in the 18th century, to have a horn light in color to the point where one could do the scrimshaw? THAT could give you the answer, alone.
Is the number of extant, surviving "decorated" horns, an overall sample, OR are they surviving because they were scrimshawed, and the more common horns were mostly lost to time? (My father has two powder horns, probably from Appalachia from say the 1870's or younger, very plain but serviceable.)
How much social pressure was there to have a scrimshawed horn? Was it "fancy" or was it considered "macho" to have a horn scrimshawed, and thus the use would vary. Meaning, if it was "fancy", perhaps the owner used it at social events like rifle frolics and monthly musters, BUT in reality when going into the woods normally carried a plain horn. (I have a pale, screw-tip horn that I use at matches and at some living history events, but when I go hunting I use a very plain, brown horn.) Perhaps the horn was a status symbol when white and scrimshawed/carved so ..., how many folks afforded such horns vs. how many would've only had a basic horn?
How does one ensure that the scrimshaw on the horn is contemporary to the horn's making?
How does one actually date a horn that has no date upon it? While there are styles that we understand were prevalent to certain decades..., how can one tell those from a more recent (though still antique) horn where the horn maker created a copy of "one that grand daddy used to carry" ?
Does artwork give us a clue to whether or not scrimshawed or carved horns were prevalent, and when? The next question on the artwork would be whether or not the image was posed, and did the horn belonged to the subject in the painting?
I'd venture a guess (for what that's worth - ain't worth much) that the average guy didn't have access to a horn that could be scrimshawed, and thus the average guy carried a plain horn. (I own one fancy horn, and three plain horns. One, fancy ones are expensive, and Two I wouldn't want to mess up a nice piece of art by busting through the woods with it on my hip)
:idunno:
LD