I'm British but living in Thailand and it's so interesting to watch the different reactions to this. Here, mask-wearing is considered a courtesy if you are even slightly under the weather and it's normal for a number if passengers on a train or one or two kids in a class to be wearing a mask at any given time. Really bad pollution means that during certain periods of the year, many more people wear masks (including children).
It became complusory in Thailand to wear masks some time ago and it remains complusory in shops, malls, on public transport (including taxis). This is relaxing slightly and I often wear mine under my chin until I am close to other people as it is super hot and gross and I don't enjoy wearing it, but I totally understand the requirement to do so. I wore one even when heavily pregnant in VERY hot, humid weather so while I know there are multiple reasons why people might be unable to wear a mask (as several posters here have detailed) I think for many more people it is a case of preferring not to.
To those disputing the science of it... I get it, there are mixed reports on them, but they certainly don't harm you (medical reasons excepted) so wouldn't you rather everyone wore them just in case they ARE a factor in reducing transmission? Worth a try, no?!
It is crazy for those of us in Asia to watch the numbers of cases and deaths in the UK and yet also see how unwilling many people are to wear a mask and to see lockdown being lifted. We've had ZERO locally-transmitted cases in 6+ weeks, the only cases recorded are in people entering the country from abroad and they are in state quarantine so will not spread the virus. The UK seems horrifying from over here!
(I'm aware figures may not be accurate in either place and I was especially sceptical of Thai data early on, but we certainly don't have overburdened hospitals or bodies in the streets, so the figures do not appear to be wildly off).
I don't understand the reluctance among anyone who doesn't have a genuine reason not to wear one. Maybe I've been culturally acclimatised to Asia more than I thought! There is certainly a sense of people here being far more biddable and generally following whatever is put in place even if they disagree, whereas in the UK (in many western countries?) there is more of a 'the government can't make me!' sort of sentiment. Or so it seems from the media and some posts here confirm that view. I wonder if I would feel differently if I were in the UK right now.
Anyway I'm rambling but I do find it interesting how differently people react to the prospect of masks...