Why do people want American and coalition forces to remain in Afghanistan?

I suspect that there are many answers to this question just because not all people think the same. In some cases I b elieve people believe that we have a responsibility to hang around after we've gone in and started making a mess with the local communities, for others it may simply be that they always agree to attack regardless of the situation, others still may have a very America-centric world view and believe that having troops overseas will eventually spread our way of life to other parts of the world.