Many illusions affect only one sensory range, maybe two. Fully sensory illusions are complicated as hell, and the mage has to actively think about evoking a fully realistic illusion. People who examine illusions closely notice that something seems “off” about most of them: the textures are wrong, light warps in unnatural ways, there’s no scent attached to the thing, and so forth. A fully realistic and sensually immersive illusion demands at least five successes and quite possibly more, especially if it’s also interactive.