Why was the Prophet, may Allah's peace and blessings be upon him, not cured of the illness of which he died, despite Aisha's ruqyah for him?

Ruqyah (definition) falls under the category of asking Allah Almighty to fulfill needs, and Allah is Generous; He responds to whoever supplicates Him. Allah possesses ultimate wisdom in choosing the type of response for His servant: either He grants him what he asked for, or He diverts from him an equivalent evil, or He stores it for him in the Hereafter, as stated in the Hadith (definition): "There is no Muslim who supplicates with a supplication in which there is no sin or severing of kinship ties, but Allah will grant him one of three things: either He will hasten his supplication for him, or He will store it for him in the Hereafter, or He will avert from him an evil equivalent to it." This indicates that supplication must be answered in one of these three ways.