Disbelievers have purposes in their lives such as collecting money and property, indulging in sex, eating, and dancing. But all these purposes are transient and passing ones. All these purposes come and go, go up and down. Money comes and goes. Health comes and goes. Sexual activities cannot continue forever. All these lusts for money, food and sex cannot answer the individual's questions: so what? Then What?
However, Islam saves Muslims from the trouble of asking the question, because Islam makes it clear, from the very beginning, that the permanent purpose of the Muslim in this life is to obey Allah in order to go to Paradise in the second life.