This is all REAL easy to explain:

When you are using a machine to stitch inside the pleats (and it's VERY easy to do)you are sewing pretty straight for the most part. You are then left to manage the taper with the angling of the pleats. This is very succeptable to pleat wandering and faster wear-out of the thread. There are MANY pictures and examples available.

When you are hand-stitching the inside of the pleats (which is an art, and NOT easy to do) you are sewing with a nicely formed curve. You manage the taper with the process, and this is why hand-sewn kilts hang so perfectly (look at the examples that Barb posted). With modern thread materials, the seams and materials suffer minimal pressure, unlike some kilts from the past.

Then you have to consider the materials:

Wool can be hand-sewn and machine sewn to look great. Wool has the natural ability to be "bent" into shape. As long as the seams are not done too tight, there is some "give" that will alleviate damage. If the seams are done too tight, there is no "give" for the seams to move with.

Other materials are much more rigid due to the fibers and the weaves. It's not always real evident to the fingers or the eye. They do not have the "give" when they are stressed. One easy example of this is with denim jeans. Look how often the knees wear-out. That's what I mean by "give" with the weaves. Yes, jeans form to the body after time... but at the expense of "opening" the weave.

If you're looking at a "casual" or "modern" kilt... machine sewing is really the only way to go. It's tough enough for the materials and makes it so that the price is affordable.

If you're talking about a "real" kilt... hand-sewing is the only way to go. The authenticity of the construction can only be done with the curving and bending. A machine just can't do that. When we say "traditional", that's not a term taken lightly. There's MUCH more to it than a tapered apron and three buckles. There's a manner of construction that goes WAY DOWN DEEP into the thing. You just can't imagine what it takes!

If you're comfortable with a machine sewn, three-buckle kilt... GREAT! The outside appearance is relatively close to the real thing. If treated and cared for properly, they can last for quite a while. Just know that they are NOT like a hand-sewn when it comes to the actual construction.

Two buildings look the same from the outside. One is constructed with wood beams and nails, while the other is made with steel beams and rivets. One is made by guys with a pattern and a cool tool box, while the other is made by HIGHLY trained and certified architects and artisans.

This is why you pay more for a properly constructed garment. This is also why I'm constantly preaching about how we should all respect the companies that make the authentic hand-sewns. Until you see and experience what it takes... you just can't imagine the skill that they have.