As far as i know, flat wings DO provide difference in pressure, because of the angle of attack. At the same time, the angle of attack also provides further lift from the downwash of the air (newtons third law).
The reason why most wings do feature complex airfoils is greater range of lift they achieve. Lift achieved solely by angle of attack has its limits, and after a certain point the drag induced by that angle becomes greater than the lift. Airfoils achieve lift with less induced drag, theyre simply more efficient.
The reason why most wings do feature complex airfoils is greater range of lift they achieve. Lift achieved solely by angle of attack has its limits, and after a certain point the drag induced by that angle becomes greater than the lift. Airfoils achieve lift with less induced drag, theyre simply more efficient.