I don't think anyone has addressed this point yet, and if so, pardon my overlooking it.

The reason a kilt is made with a high rise in the first place is not just for looks. A kilt is a heavy garment. Even a 4-yard, 13 oz. kilt weighs more than the average pair of jeans. With jeans, you have a belt to help hold things up, but even then they will tend to sag a bit as you move through your day. Kilt belts aren't really going to function this way, even if you do thread them through the straps (a definite no-no, but that is another conversation entirely). So now you have this very heavy garment, with no real help from a belt, with a sporran and all that loot in it, and the force of gravity figured in. See where I'm going with this? Having the top strap pull the kilt taught into your real waist, above your hip bones, and suddenly there is no problem keeping all in order. I've tried the "jeans cut" version, and quickly rejected it as a bad idea.

Gravity isn't just a good idea. It's the law.