Growing up in Scotland (Coatbridge, ya bass!), kilts were conspicuous by their absence.
It is not the Scottish national costume, but that of the Highlanders (teuchters, or illiterate people who habitually marry their cousins).
People from the Lowlands (the vast majority of the Scottish population, centering on the Glasgow-Edinburgh Corridor) wear Trews (think Levi 501's made of tartan) as their ancestral costume.
Very few people choose to wear either, for the same reason few Italians wear togas or tunicas these days: it looks anachronistic.
If you want to get in touch with your Scottish heritage, buy Irn-Bru* by the case and eat deep fried Mars Bars.
*- http://en.wikipedia.org/wiki/Irn-bru