Not quite 20 years ago, was there two summers ago at St Andrews, and at least a weekend twice a year on family business. While I would agree that Perth would be a likely place to have seen this, it is just possible that if you went back to the same store you would have seen none. For the same reasons probably, one is more likely to see national dress here in a small town or village instead of Palma.
In either case, it is a matter of dimension, the typical Scottish male of today must rent a kilt for a wedding or social event (not counting SC or H dancing), this makes it a folk costume and not clothes.
BTW, a few years back, I got attacked for the same logic, when I was attending an Indian powwow in southern California (none of the tribes represented were of California, and Souix were the majority). I was told that these were not costume, but native dress. To which I asked how many were in attendance compared to all the indians of his tribe in Southern California, answer about 1%. To which I suggested that if the majority of the other 99% did not own "native dress" or wear it in the course of one´s daly life, then it was a costume (easier for Amerinds, because, unlike the Scots, the women´s costume is more commonly seen than the mens).
The local, Malloruí, equivalent of being Scottish by wearing a bit of tratan, is found here with neckerchiefs (boy scout type of triangle, with no slide). On some feasts even the priest and altar boys wear them during mass, choirs commonly use them as the only uniform part of their uniform, as do teams and fans. They are almost the equivalent of fan t-shirts in the U.S. Besides around the neck, they are used as belts, arm and leg bands, and while girls wear them on their head as any scarf, men often wear them as an accessory to our local costume (sort of Pirates-of-the-Carribean), for men, except the foot wear for dancing groups are two tone brown and white golf shoes (socks are such an option here, that at an important mass, one can identify the bishop because he is the one with black shoes and socks, all the others look like Franciscans..