If by Imam you mean a leader, I think every human being and every civilised society agrees that every group of people with a common goal need a leader to coordinate all the tasks and to guide people towards their goals with the best of his/her abilities.
However if by Imam you mean a divinely appointed person who is supposed to be there for us after the death of the Prophet (sws), then I should say there is no need for such a person and in fact there has not been such a person after the death of the Prophet (sws).
The Qur’ān has made it clear for us that after the Messengers, we do not need any other live and divinely appointed guidance and that the delivering of the message of Islam has been completed at the time of the Prophet (sws):
(We sent) messengers as the givers of good news and as warners, so that people should not have a plea against Allah after the (coming of) messengers; and Allah is Mighty, Wise. (Al-Nisā 4:165)
This day have I perfected for you your religion and completed My favour on you and chosen for you Islam as a religion. (Al-Mā’idah 5:3)