//…their spread can be inhibited, i would call that containment//
They cannot (unless everybody is isolated from everybody else – permanently). All that can be said is that the spread can be delayed. Everybody, probably worldwide but certainly is this country, is likely to be exposed to the SARS COV-2 virus multiple times in their lifetimes (unless they isolate themselves permanently). Just how their bodies deal with that exposure will vary from no symptoms whatsoever to death. To be clear, isolation means complete isolation; no family “bubbles”, no “rule of 6” or any other of the nonsensical arrangements that were variously bandied about during the Covid fiasco.
//…the vulnerable cannot protect themselves if nobody else does anything//
Yes they can. As far as face coverings go they can use FFP2/3 standard masks which, if worn and treated correctly, will give them more than 99% protection from airborne viruses. There is no need for anybody else to do anything for that to be achieved. If that is insufficient for them, they can isolate themselves away from everybody else as far as possible.
//…it is however quite possible for new variants to put us all back to square one so a tiny but effective like wearing a mask does not seem like much to ask for most people.//
The risk of new variants of viruses evolving is constant; they all evolve and mainly they do so in order that they do not kill their hosts. Therefore, the question arising from your statement is “for how long do you consider this should go on?” Every few weeks a “variant of concern” is identified along with the usual bloodcurdling warnings from the experts that masking up is necessary. As I have explained, reducing general exposure to viruses (of all types) is not beneficial to the human immune system. One of the unwanted side effects of the attempts to do so during the pandemic was large numbers of people going down with ailments that previously their immune system would have coped with.
//..wearing a mask does not require an otherwise healthy person to put anything in your body, shoulder any significant expense or do anything of any significant physical difficulty…//
No it doesn’t involve any of that and we’ll leave aside the general inconvenience of wearing a face mask and the undesirability of doing so. However, as I mentioned in a few threads during the pandemic, my cousin is the nursing director (AKA “Matron”) in a large general hospital. She has spent more that 35 years in nursing, much of it in A&E and theatre work. She has forgotten more about PPE than most of us will ever know. She was appalled by the mask mandate which compelled people to wear an unsuitable and ineffective face covering when many of them did not adhere to the proper discipline that goes along with it (e.g. wearing it properly, not stuffing it in your pocket, hand washing before handling it, changing it regularly). The plain fact is that the majority of people who wore flimsy face coverings were providing no particular benefits to themselves or others and in fact were usually jeopardising their own safety.
//…it is quite literally the least you could possibly do.//
But the question really is, why should you do it?