The failure of the scientific literature to support medical masks for influenza and all other viruses, is also why Fauci, the US Surgeon bloke and WHO, and pretty much every infectious disease expert have stated that wearing masks won't prevent transmission of SARS CoV-2. Although WHO later changed their recommendations, the science did not change, nor did new science appear that supported the wearing of masks in public not at the highest available evidence. In fact, the most recent analysis once again confirms that masks are ineffective in preventing the transmission of viruses like Covid
https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
The Equalities Act allows those to claim exemption that is why folk cannot be challenged. The risk that the wearing of face coverings will also likely increase viral transmission due to fannying about with it, touching it, adjusting it etc then chucking it on the pavement. Potential harms to the wearer have also been highlighted including exhaustion, headaches, facial dermatitis, hypoxia and dehydration.
There are also those with some mental health difficulties who are likely to find that face coverings increase their emotional distress like panic attacks, thoughts of suffocation Also, some have had physical and s3xual assaults, that involved some form of smothering or a hand over the mouth, this may trigger ‘flashbacks’ of the trauma by the physical sensation of a mask.