To better understand my question, look at this A320 below

As you can see, the wing becomes parallel with the airflow at the wing root. Same thing on this 737

But this is not found on bigger planes like the 747 or A380. What is the propose of this?

To better understand my question, look at this A320 below

As you can see, the wing becomes parallel with the airflow at the wing root. Same thing on this 737

But this is not found on bigger planes like the 747 or A380. What is the propose of this?
