I partly agree, like if you have sensitive images like nudes or other stuff you don’t want others to see, then put it in a protected folder requiring your password just to be safe. There’s also the fact most phone image viewers also have previews of other images at the bottom, so the other person could accidentally glance and see a faint icon of a dick or whatever and still find it a bit weird.

Then again though, if you hand someone your phone to see a single image, and that person feels it’s their right to see your entire photo library, to say it directly, they’re an obnoxious dickhead.