Is a belt required for a kilt?

[MikeC]

I was looking at pictures of Prince Charles and his style when he wears a kilt. I noticed that he doesnt wear a kilt belt. Most of the pictures of him are with a jacket and vest, but there are less formal pictures, and he isnt wearing a belt then either. I know that a belt isnt needed to keep a kilt up (on). So, what is the thought about wearing a belt? Is it necessary? When is it not? When is it required?

While i mostly wear a kilt casually, i find that I dont usually wear a kilt belt. All 4 of my kilts are 8yd "traditional" kilts, no utilikilts, or modern cargo pocket kilts (i personally dont care for them).