While a handy pair of sunglasses can dress up an outfit, members of the royal family are largely discouraged to wear them owing to the way it can cause issues in their interactions with the public.
As per etiquette expert Myka Meier, while speaking to People, royals are only ever seen wearing sunglasses during sporting events or an outdoor activity.
According to Meier, the royals primarily use it for sun protection but will take them off as soon as they are indoors.
"Sunglasses — or 'sunnies,' as they are called socially in the U.K. — can be seen on royals during official engagements, but usually only during sporting events when there is an activity or event outside or when needed as eye protection for a sunny climate or environment they are in (think Kate on her royal tour in the Caribbean)," Meier said.
"They will remove sunglasses as soon as they walk inside, have a prolonged or serious conversation or upon any formal greeting."
She added that as per royal's dress code, wearing sunglasses in a setting that does not warrant it comes off as disrespectful.
"Sunglasses don't allow direct eye contact, which can be seen as a barrier when communicating," Meier said.
"By taking sunglasses off upon meeting, it is seen as a sign of courtesy and respect to the other person."
Kate Middleton was last seen wearing sun glasses as she witnessed Prince William participating in a charity polo match.
Prior to the game, she placed them on her head as a headband and chose to remove them completely when awarding her husband and others with post match prizes.
Queen Elizabeth II was said to be a fan of wearing dark shades.
The late monarch reportedly chose to wear them for outdoor garden parties at Buckingham Palace but would always take them off the minute she was indoors.