Currently, exit rows don't have window shades so you can see if one side of the plane is on fire. Don't laugh, people have died because of this problem. However, if all rows had their window shades open or even half way open, escaping passengers could see ahead of time if one side was burning.

I talked with a FA who agreed that opening the shades during take off and landing is wise, but not required.

I recently sat next to a very militant woman who refused to open the shades when I explained the reason for my request. I even told her that closing them for the main part of the flight was fine.