A royal source explained the decision to forego face masks, telling the Mirror Online, "Specific advice on this visit has been sought from the Medical household and relevant parties, and all necessary precautions taken, working closely with Dstl."
The source added, "All Dstl staff have also been involved in the UK’s response to Covid-19 so are well versed in the necessary precautions."
It does seem like the risk of the virus being transmitted during the visit was extremely low.
The royals made sure to practice social distancing during the engagement, keeping 2 meters apart from others. Plus, according to the article, all of the staff who came into contact with the Queen and William tested negative for coronavirus before the visit.
Although the risk involved in this particular event might be minimal, many are still upset with the Queen's decision, especially considering what kind of example it will set for the rest of the population--those who do not know just how many other safety measures were taken for the engagement.
Piers Morgan tweeted, "Why no masks or social distancing? Sorry, but this is not a smart move by the Royal Family as the virus rages & the country heads into another lockdown."
Omid Scobie, the writer of Finding Freedom, also commented on their lack of masks. "My two cents: While sensible and safe precautious were clearly made, I do worry that most people seeing the photos/videos won’t know the back story. As the majority of the UK enters tighter restrictions, seeing leaders in masks would have been a strong visual," he tweeted.
Another user wrote, "Why can’t these ‘Leaders’ see the harm they do by not setting an example for the people they are supposed to be leading ? It’s irresponsible and downright STUPIDITY!!!"
The royal family has not responded to these critics, but hopefully they'll take it into consideration and put masks on before their next public engagement.