Why Western troops in Afghanistan are they?

It seemed to me that the purpose of the mission was "to capture bin Laden dead or alive." Since it is no longer of this world, and had not set foot in Afghanistan for over five years, one wonders why it is there. After all, if the Afghans do not want democracy and prefer an Islamic regime, it is their right ... just make sure there are no training camps for terrorists but services special satellites and drones perform this function very well.