Besides the fact that it is mentioned in The Holy Quran as part of accountability concept, the simple logic is that how do we learn about such concepts? We learn from our parents, friends, media and other sources. Similarly such things as life in the hereafter we learn from God’s prophets. Prophets are considered as role models because they were the most righteous people whom God chose to reveal His message. So if a righteous person makes a statement, we accept it as truth. So all prophets of God told this thing that there is a Creator of this universe. He created us and we will return to him. If there is no hereafter, then this life has no meaning whatsoever. So besides the fact that it is repeatedly mentioned in The Holy Quran, the simple argument is that there is accountability in the hereafter as there is accountability of our actions in this life. This is a very powerful tool to be better in this world for reward in the hereafter.