I would say it is a combination of those factors, Peter. Even for those who know about them, the fact that they are not stock supported by the mills means they are going to be a bit more difficult for the average person to obtain. Even though having a tartan custom woven for you doesn't have to be as expensive as many people perceive it to be, it does require a bit of extra cost and effort. And in my experience, few people are going to go the extra mile of having a tartan custom woven simply because they like the design. For the most part, if they are going to the trouble of ordering something custom, it is going to be a tartan that has personal significance to them (i.e. a clan or family tartan, or something else for which they have a connection).

I mean, I went through the effort of recreating the tartan worn in this 1859 painting, "Sheep Washing in Glen Lyon."


(The colors turned out a bit lighter in the cloth than they appear in the painting, but I'm happy with the way it looks nonetheless).

I'm a "tartan geek" though, and I think things like this are pretty cool. :-) I recognize the fact that I'm in a minority. Plus I'm in the business. I get my cloth at wholesale pricing and I make my own kilts. Which means it can be relatively easy for me to follow a wild hair and do something like this. If I was paying regular retail pricing for a custom weave of tartan, plus paying a kilt maker to tailor the kilt for me, I certainly wouldn't own as many kilts as I do and I sincerely doubt I'd own this one!

So yes, I think it is partly just people not knowing about the existence of these tartans, but more than that I believe it is the unavailability and the cost, coupled with the fact that people will always give precedence to tartans that "mean something" to them.