Kilt Klutter! A great term there Jock!

For myself, it's probably in part a "less is more" aesthetic but moreover sheer laziness, as I scurry off to pipe at a church gig or funeral or what have you.

A reason for everything, though: the jacket fits better without a waistcoat or belt under it, the kilt hangs better with 2 buckles, and as for kilt pins I don't like the idea of punching holes in a perfectly good kilt. Less kit, but everything of the best quality I can find.