It only really made sense as a way to give slides meant for human viewing, computerized data for sorting, filling, or otherwise using simultaneously with the slide. Like, a picture of an engineering diagram, patent, survey site, military target, etc.

Before we could store a picture as raw binary data, this was an interesting way to fill the need to digitally notate images. Punch cards like this were definitely in use for a while. I have a post above with an image.