A no brainer that wearing a mask in closed quarters would perhaps prevent someone from catching one's germs if they are sick. Is their a study that needs to happen to educate about common sense? If one travels and spends time in Japan, those folks seem to understand common sense.
The fact you wrote “perhaps prevent” is why the study is absolutely needed, if masks ever come back they’re going to get the same (if not much more) pushback as before, being able to say “masks are scientifically proven to prevent infection by x%” will get a much better use rate than “masks may perhaps prevent…”.
The major resistance to masks from day 1 has been that no one has provided scientific evidence of how well they work. If it’s 1% many people still won’t think they are worth the discomfort but if they can show it’s something substantial like 20% most people, even anti-maskers, will get on board.
The success or failure of future mask mandates completely depends on them showing evidence they make a significant difference, common sense they “help” won’t cut it.