Though you're mostly correct (about it being a social thing - and I'd use SARS in asia for comparison), people coughing for any reason in public should be of concern. This coming from a heavy smoker who's lungs are a phlegm factory.

Could be allergies, could be anything, including a germ. A cough, or two, into your arm is one thing, fine. Being a walking cough machine is another; socially speaking, despite what you (the cougher) may think/know.

I'm not shaming anyone F2F. This post is not shaming so much as calling common sense into question. And, FWIW, you're right; it is simple. Like carrying a gun, protecting oneself is a personal responsibility. Just stay outta my space and we'll be fine.