Actually, any technique may be performed from any stance. However, some techniques are more suited to certain stances.
When you stand still, you become a target. When you stand still while squarely facing your opponent, you become a big, inviting target. The walking (front) stance is a good all around stance for stability and it permits maximum application of power in an attack, but, to use it, you are squarely facing your opponent which exposes a lot of targets, so it is rarely used in sparring except maybe in traditional karate style ippon sparring. When sparring, or for self-defense, the walking stance is best used with the finishing blow when the opponent is weaken or off balance.
When fighting, stances are rarely stationary; they are always in transition. Stances only exist for a instant while you are in the process of moving from one stance to another or while you are executing a technique.