Same people in a plane for three hours unmasked, same people in a bus for ten minutes masked, same people plus the contents of dozens of other flights queue for immigration unmasked.
When all else fails, fall back on Sesame Street: ‘one of these things is not like the others’
In a way - exactly. When on my Camino, 4 of us Pilgrims stopped at Decathlon on the outskirts of Burgos. We then inquired as to how far to get to the Center and were told that there is a free bus going from this Shopping Center to the center city.
We went to the stop and for close to 30 minutes were surrounded by and happily conversed with many others (mostly locals) who was waiting for the said bus. In cases of those who was sitting on the bench the distances between us were dismal... may be a foot (so like 30cm?).... all unmasked....
And then the bus came up and everyone put the masks on.....

Y!!!!
Now. I am also one of the folks who follows the rules and I dont argue "the rule is the rule" thingy... I am merely pointing out (just like
@henrythedog ) that sometimes things are just... work out silly if you look at them from the side.
If the face mask is optional - then by all means it is up to a given particular individual whether to wear it or not based on their beliefs, situations, etc. There is absolutely NOTHING wring with that!