As a social animal we have to take account not only of the risk to ourselves but also the risk we might pose to others.
I'm sure that the Individuals who went on a night out in Aberdeen or Bolton or wherever thought that the risk was to them, not from them because they did not realise that they had an asymptomatic infection. They decided that their need for a Life was greater than the risk to them. Unfortunately out of the hundred or more that they infected, directly or indirectly, some will have become seriously ill and may not ever fully recover due to damage to their vital organs, including the brain. That cost falls on the wider community.
There are two good reasons for wearing a mask wherever it is required.
The first is that it blocks the larger droplets emitted when we cough or sneeze. The other is that it is a badge of our commitment to the wider community, just as refusal is also a badge.