It's probably because you're expecting the kilt to sit at your jeans waist and not your true waist. The traditional Kilt is really meant to be worn much higher than jeans and your rise is probably correct. If you hem a kilt, the selvedge looks odd. THe correct way to lower the rise is from the top and this can be costly.

Steve Ashton (Wizard of BC here) owns Freedom Kilts. If you really want to wear your kilt on your hips rather than at your true waist, he can make you a kilt that is designed for just that.