Can this be a US centric problem? My thousands of flying hours on EU3 metal have never been crossed by a request to shut the blind on a day flight, although I do close it for an "overnight" even if it's day light outside. Maybe we're not quite so superglued to a screen over here and the eye shades I have used when I've wanted to doze have been quite acceptable in letting no light in at all.
It depends where you're sitting on the plane too. Especially if you're on/just behind the wing, the glare reflecting off the wing can be pretty strong. On a recent TATL I had the 'amusing' experience of going almost blind when just looking to my left. I think the whole row sighed relief when I (politely) asked the lady in the A-seat of my row to close her shade. She had been so occupied by her book that she had not once looked up or noticed the bright lights.
Don't understand why someone would ever need an FA to make such a basic request of a fellow passenger.