I began making kilts with only two straps for the kilts we are making for the Canadian Scottish Regiment. I also eliminated the strap hole on the left side, putting the strap and buckle on the inside.
This was because the regimental kilts are kept in stores and issued as needed. Not having the strap hole allows us to re-size a kilt in just a few moments.

We now make almost all our Kilts with 2 straps and the left on the inside. It has saved our customers money if their kilt needs re-sizing and in my opinion allows the kilt to hang much better.

We can keep the full strength of the stabilizer and interfacing intact. No weakness at the strap hole.

Leaving the third strap off has also virtually illuminated any distortion of the outer apron fabric by an owner who tightens the third strap thinking that if it is there, it must have a function.

Some of my older kilts still have three straps and buckles but I have caught myself forgetting to fasten the third strap.