In my store we get so many customers not wearing a face covering but wearing one of those sodding sunflower lanyards and declaring to all and sundry, and usually quite rudely 'I'm exempt!
There isn't any testing to determine if someone should be excused from wearing a mask, the lanyards are available to be purchased from supermarkets.
I would have thought that should you have a condition that precludes wearing a mask such as asthma or COPD the last thing you would want is a deadly virus that attacks the lungs!
One of my colleagues has asthma and she wears a mask during her shifts, not only to protect herself but to protect everyone else as she has a six year old germ factory daughter in primary school and I have a good friend, a cancer survivor who has COPD and he wears a mask as soon as he steps beyond his garden gate.
We notice though that a lot of people wearing sunflower lanyards walk down the street either smoking or vaping....