When I first got first kilt, I wore it with both the sporran strap and the belt through the loops. It took less than a month before I stopped using the loops for the sporran strap because my hips and rump held it in place just fine. Running both through there was also bulky and cumbersome, and I was always worried I would warp (or worse rip) the fabric.

Shortly after that, I stopped using the loops for the belt, too... for no real reason other than I got too lazy. Now I rarely wear a belt at all, unless I'm wearing my USAK casual out and about... and that's only because I've lost several inches since I purchased it and if I don't wear a belt the excess apron flaps wantonly off to the side. For that kilt, I use the loops Rocky provided.

I think we're so accustomed to seeing loops along the waist of our garments designed for belts that it only makes sense to us to run the belt through them... and it looks sloppy at best or even just plain weird if the belt is run atop instead. And even if not to us, it does to other people.

To each his own, though, and wear it how you see fit! For me, any bespoke kilt I order in the future will be made sans loops, and I won't be using them on the ones I have.