The “prepper” mindset was rampant in the 1960s because of uncertainty and fear around nuclear war. Radiation detectors would have been still costly for the average Joe, and this allowed people to feel some level of preparedness.
It's hideous but it's a sort of psychology that makes sense to me. You're faced with this overwhelming existential threat you can't really understand. And here's a cute consumer device marketed to you to that promises to give you some idea what might be happening. It's a way of establishing the feeling of control, even if it doesn't work very well.
No, having some radiation indicating device is a lot better than not having one. It at least shows when it's safe to leave your basement for a short while or not.
