To make the dimwits feel safe. Those who take public transport, those who are customers. Many of them are 'true believers' who self-test at least once a day. If you present them with a new booster they will take it.
From what I read, masks remain required in specified healthcare, education, transportation, and congregate settings. So, those staff doesn't have another choice. On one hand, I feel sorry for them as I know what it is like to spend the whole day wearing a mask. On the other hand, I had Covid about a month ago and felt bad. Fortunately, I had Canadian Pharmacy meds that worked for me. If the masks really lower the risk of catching the virus, I hope they work for them.