Planes use flaps to land and to take off. So why do they retract them while they are on the ground, ie why not just leave them deployed?

Question

Planes use flaps to land and to take off. So why do they retract them while they are on the ground, ie why not just leave them deployed?

In: Engineering

Answer 1

All the reasons everyone has given, but also: taxiing with your flaps down at the very least used to be a signal for hijacking. It possibly still is. I know if you for any reason are going to be taxiing with your flaps down you must notify the tower.

Source: https://www.latimes.com/archives/la-xpm-1986-03-13-mn-19547-story.html