When looking at a card with images in a files field, the images do not fit to the size, instead they go out of bounds. I don’t see why anyone would NOT want to have the images fitted to the viewport of the field.
The cover image in board and gallery view has the setting yes and does the job, but I would like to have this setting for the individual field when looking at a card with images in a files field. However, both for cover images and field images, I have a hard time understanding the use case for images that goes out of bounds. So in both cases I would rather have it always fitted to the viewport rather than with a setting (that has the wrong state by default).