1. To Test the Faithful Based on Islamic sources: Testing the creation and choosing the righteous ones of them, is one of the constant traditions of God. Life is full of tests for the pious whom use it to nurture their faith, patience and obeying of God's commands and reach perfection by flourishing their talents and abilities. Imam Mahdi's occultation is a means to test; as the facade falls from the people with instable belief, their doubts and uncertainty shall take over, while those whose belief have rooted into their hearts, shall become more experienced and worthy in faith and reach higher levels of piousness and divine reward, as they bear through the troubles of time etc
2. To Save the Imam's Life: A look into some narrations suggests that God saved the Imam from the danger of being killed, by occultation, for had he appeared from the very beginning of his life, he would have been killed.
3. Being Free from Accepting the Leadership of the Illegitimate Ruler: According to some narrations, the twelfth Imam shall not recognize any oppressive government, even as a dissimulation. He is not obliged to perform Taqiyya for any leader or king, and shall not live under the flag of any oppressor. He will perform God's rulings with no compromise, concern, or secrecy. In other words, he will be in occultation until he rises and thus be free from allegiance or loyalty to any leader or government.
Sheikh Nuru Mohammed