I have no issues with people having the shades up during the night and they should have on descent and take off. But some people do not understand that the direct sunlight might not be in their eyes but the angle and also the glare of something else could get into another passengers eyes. There is a reason why the crew goes around asking to put the shades down during long cruise on long hauls. I have never seen them do it during short flights especially during daylight. And for motion sickness I do understand that as I have it too sometimes but looking out of the window makes it worse for me and I feel claustrophobic wearing an eye mask.