@Nico, any very tall or wide image that contains text.
Typical example could be web comics; typically intended to be viewed on a smartphone: width is limited to that of the screen (something like 400 ~ 500 px), height is given by the content and has no limit.
Resizing 5000x5000 to 2500x2500 is ok, because the image is seen anyway at about 400x400.
Resizing 400x5000 to 200x2500 would mean the image is then seen at half of the intended resolution, pixelating it or, worse, making the text unreadable.
But hey, it was just something to consider… or not.