The normal 2.5" and 2.25" belts are specifically due to the waist width on a real traditional kilt. That way, the kilt stays rigid and does not slip down. When I'm moving alot onstage, I DO tend to drop to a normal 1.5" belt so that I don't jab my ribs.

Many of the modern kilts are quite fine with a 1.5" belt... and even look better without all the leather bulk of a kilt belt. BearKilts (atleast the ones that I have) ride on the hips and actually look MUCH better with a standard belt.

The 3" belt is a "Piper's Belt". It's worn through the lone belt loop on the back of a Piper's Kilt, and hangs pretty freely. There's really not much of a call for one, other than being a Piper.

Of course, you can always avoid a belt by wearing a waistcoat and sporran. That's the REAL lazy way out of having to get a belt!