They are just simple.

And what they do is very fully exploit the analog physics to yield high data density mere mortals can make effective use of.

And they make sense.

In my life, text, bitmaps and perhaps raw audio endure. Writing software to make use of this data is not difficult.

A quick scan later, microfiche type data ends up a bitmap.

Prior to computing, audio tape, pictures on film and ordinary paper, bonus points for things like vellum, had similar endurance and utility.

My own archives are photos, papers and film.