There is an airworthiness directive on the flaps. Operators have chosen different ways to comply with it.
We must visually inspect the flaps in the configuration we will use for takeoff prior to flight. This can be done during the walk around prior to a flight, or by visually inspecting them from row 12 inside the cabin. Anytime we move the flaps, we must make an inspection.
So, it is easier for us to set them to flaps 8 or 20 after landing, and look at them during the walk around, and leave them in that same position for takeoff. It's a pain in the rear, but it's the way we must do it.