Here's a simple question: why is it the experts and citizens in the likes of Denmark, Norway and other countries in here are saying that wearing a mask is not the default choice? Their politicians have dealt with the crisis better. There's clearly no argument that they put public health second. So if things were as simple as you're portraying them, masks would be the obvious decision in all scenarios.
There is absolutely zero doubt scientifically that wearing a mask reduces virus spread. Of course, only the high-end masks (that only designated people can get their hands on) block over 90% of virus particles, which is MUCH lower for the cheaper and cloth masks. But every little helps. Also, wearing a mask is more about protecting others than yourself: virus particles can still enter through your eyes and ears if you wear a mask, but at least some of what you breath, cough, etc. out gets blocked.
Why it's not mandatory anyway: because of what happens when people have to wear masks. People with masks tend to feel safe and no longer sufficiently take all the others precautions (like keeping their distance - which is more important than wearing a mask in well-ventilated and outside areas), and people wear masks wrong, keep fiddling with them and thus touching them and their faces, and so on. Also, making masks mandatory can lead to social tensions.
Governments have to balance these pros and cons and figure out a balance. In most places in the west, that now have limited numbers of cases and no tradition of wearing masks, that tends to result in stuff like 'strongly recommended', and no more. It is easier in Southeast Asia, where people are more used to wearing masks and people tend to be more sensitive to arguments about 'for the good of society'.
So yes, I think you can reasonably make this into a moral issue. If you are well-informed, care about the wellbeing of people around you (if you don't care to get sick, they might), and can muster the discipline of wearing a mask properly, then I think you arguably have an obligation to wear face masks when you're in crowded or indoor areas.