It's interesting to note that in the early decades of the tailored "little kilt" it was considered a working garment. It was indeed "fatigue" dress in the highland regiments. The belted plaid was the more formal, "dressier" item of highland garb.
Now it's been largely relegated to costume status, though it certainly can still work quite well for formal occasions, as Mr. Killman's photo shows. I believe Matt Newsome also has some pics showing the belted plaid looking great in a "modern" context....