Loops started out as something to put the sporran strap through so that it wouldn't feel like it might be headed south as you moved around. This is really only an issue if you have a flat kiester. Most people have cheeks big enough to keep that from happening.

A belt doesn't need loops, because it's solely decorative, it isn't used to hold a kilt up, and it's unlikely to fall down. Despite that, sporran loops are commonly made big enough for people to put belts through, and people do call them belt loops. I try to talk people out of putting a belt through the loops, because, over time, it pulls up the bottom of the kilt directly under the loops and distorts the bottom line of the kilt. If you don't believe me, just have a look at a well-worn kilt (e.g., a band kilt) at the next games you go to.

Barb