A shot I took in Tokyo on a train in late 2019 not too long before the COVID-19 pandemic — although Asia is generally known for being ahead of the curve in mask adherence even during normal times, no one was wearing masks during this particular train ride.
Masks and mask etiquette have become the mascots of the COVID-19 epidemic and we are starting to see vaccines trigger a renewed discourse about whether it is even okay to skip wearing a mask outside. The following is my attempt at outlining an etiquette bridging the gap for wearing masks in the future, pandemic or not, with the goal of introducing mask-wearing as an appropriate norm.
Assumptions
Wearing masks can help prevent the spread of certain airborne illness or at least make the illness more mild (although cloth masks are less effective than medical-grade masks).[1]
Though some diseases whose spread would be stopped by a mask can be deadly, most are generally are not.
Although the cost of wearing masks is not high, it is not zero, and even if they can be well-designed fashion accessories they also can introduce awkward situations when mandated or expected -- forgetting a mask, masks not fitting well, or trying to work out or do strenuous activity can all be a little annoying. Plus, sometimes you simply don't want to wear one.
The shaming of individuals into wearing masks in all situations beyond reasonable caution, particularly outdoors, is undesirable for this reason.
Proposal
Rather than dismiss the benefits of mask-wearing, this proposal will attempt to balance the desires of many to have the option to not wear masks and "return to normalcy" with not dismissing the benefits of masks outright; returning to normalcy doesn't need to mean not learning anything from our experience, but knowing there's some statistical reduction in disease transmission doesn't mean there aren't other tradeoffs associated with being germophobic in this way.
Touching and being close with other humans in shared experience is nice, smiling at people and breathing without obstruction is nice, and in general shaming other people one way or the other should not be a first resort.
General
In general, etiquette is always subject to specific changing conditions. For example, let's say there's a deadly airborne COVID-23 in a few years (god forbid) and it appears to be mitigated to some degree by masks, although the evidence is not 100% clear yet. I think it would be incumbent upon folks to wear a mask while the data is being collected, even if it was not clear how deadly the disease was.
Specific situations matter. An outbreak in Tanzania does not mean everyone in Texas must mask up immediately.
If, for example, there were a pandemic with a virus that was easier to transmit outdoors, then the etiquette in the Outside section would need to be modified appropriately for that time. Or, if you knew there was a bug going around your office or your city, it may also become advisable at that time to encourage mask-adherence.
Outside
People who are not sick and don't suspect they're sick (with anything) should not be shamed for not wearing a mask in normal situations outside, particularly if vaccines have been available for enough time for the most vulnerable and then some to be jabbed.
For super-crowded outdoor situations, they probably just shouldn’t occur if there’s no vaccines (or its’s early in the vaccine deployment) and the pandemic is worrying enough. If they must occur — let’s say there’s outdoor queues for essential events or processes like air travel, groceries, or medical services — then it is fine to enforce mask-wearing.
People who do choose to wear masks outside shouldn't be shamed, because they have a right to be extra cautious, or to thinking they might be coming down with something, or they're on their way to somewhere indoors and they haven’t got the time or inclination to take theirs off, or they enjoy wearing one, or any number of other reasons that are none of your business.
Inside
During active pandemics, people should probably keep wearing masks inside for a bit longer than they might otherwise want to. Give some time for people to get vaccinated and avoid giving anti-maskers/anti-vaxxers a social hole to weasel through.
If you're actively sick and must go somewhere, wear a mask!
If you suspect you're getting sick, still wear a mask!
Similar to the final point in the Outside section — if you know you're going on an important trip soon or any other reason you don't want to be interrupted by sickness, or even if you just want to, it shouldn't be considered excessively weird to wear a mask indoors if you want to during normal times.
Final Thoughts
Basically, while a COVID-19-like pandemic is edging off and vaccines are still being deployed with considerable uptake in your country (or haven't been deployed yet), it isn't a bad idea to keep wearing masks indoors by default. It should continue to be encouraged for people who think they're coming down with something, and totally fine for people who just want to avoid getting sick for whatever reason.
Wearing a mask outdoors has always been iffy and should not be an expectation ever (except perhaps during the beginning of a pandemic when there may be unknown unknowns at play that need to be given due caution), but also shouldn't be shamed for people who choose to do so.
Footnotes
There's a lot of different studies and meta-studies on the topic with various results, and I don't claim to have perfect knowledge on the subject, but generally mask wearing seems to be better than no mask wearing -- one interesting thing to note is that even in cases where folks get infected while wearing a mask, those infections may be reduced to mild or asymptomatic on the basis of receiving less initial viral load (because of the filtration of the mask), which is even more reason to encourage mask-wearing.
At time of writing, I believe in the USA we are currently exiting the period where this would be reasonable. To be frank, by end of May 2021 I think any person or organization requiring (or shaming) folks to wear a mask for an optional outdoor event like a concert or even a crowded hike is going too far.