Rear windscreen wiper usage - some thoughts

Over the last 25 years of driving I've noticed something, and my family are sick of me pointing it out all the time. I'm going to vent here in an effort to purge myself, as I can't help pointing this out every time I see it.

Maybe I'm wrong and would welcome opinions to the contrary, but I would assume most drivers would only use their rear-windscreen wiper just before or as they were checking their rear view mirror. However, every time it rains I'll see someone with it going on/off/on/off constantly in the same way they might use their front windscreen wipers. Unless it's broken, I can't help think it's the biggest red-flag that someone is either a very nervous or very inattentive driver. It immediately makes me increase my distance from them and frankly pisses me off somewhat. How could you not find it irritating to have the rear-windscreen wipers constantly going or do you genuinely not notice them squeaking away - in which case how inattentive must you be to your surroundings whilst driving a car? Or do you not trust your own co-ordination abilities enough to use the rear-windscreen wiper on an on-demand basis? Do you need to automate it as the alternative would be too tricky a task to perform whilst driving, like juggling on a unicycle? What faith, then, should I have in your abilities to manoeuvre a moving vehicle in any circumstance?

At least 10 times I've seen someone driving around with their rear windscreen wiper going constantly - WHEN IT ISN'T EVEN RAINING.

I feel like this has become my old-man obsession and by sharing it I'm passing it on, like a haunted photograph.