...,but my point in my previous comment ..., suggested that precisely it seems that the transparency film is now subtracted from that great value ... of that past period, and only remains the slide/protection relation argument, not leaving another space in the understanding or reasons - for some people - to use them.
I already hinted at that point, but showing a slide/transparency on a light table, if actually a print is the final aim, is technically not sound.
But is likely a means to persuade a less initiated person.

