So that's why.

Whenever pictures are shared of Prince George, whether it's a Royal outing or simply at home with his family, he's always wearing shorts. We've never thought too much about it and why he constantly wears them but it turns out there's a very specific reason for it. Yes, when the Royal Family released this year's Christmas card, the question about Prince George's clothing choices came up yet again.

"The image features on Their Royal Highnesses' Christmas card this year," captioned the post. "The photograph was taken earlier this year by ChrisJack_Getty at Kensington Palace."

The Duke and Duchess of Cambridge are pleased to share a new photograph of their family. The image features on Their Royal Highnesses' Christmas card this year. The photograph was taken earlier this year by @ChrisJack_Getty at Kensington Palace. pic.twitter.com/p8jm6zDfl0

— Kensington Palace (@KensingtonRoyal) December 18, 2017

The young royal has never been photographed in anything other than shorts, and many are praising the four-year-old's commitment to the trend. However, it's not just his go-to style choice, it's actually one of the many royal traditions the future-king has to abide by.

I appreciate Prince George's commitment to his personal brand which is champion of a formal short. https://t.co/4zU8N8rR5H

— Sean Maguire (@SeanMaguir) December 18, 2017

According to etiquette expert William Hanson it's got to do with tradition among the upper class, aristocracy, and royals. If they were to avoid this tradition it would be seen as "suburban".

William told Harper's Bazaar: 

"It’s a very English thing to dress a young boy in shorts. Trousers are for older boys and men, whereas shorts on young boys is one of those silent class markers that we have in England.

"Although times are (slowly) changing, a pair of trousers on a young boy is considered quite middle class – quite suburban. And no self-respecting aristocrat or royal would want to be considered suburban. Even the Duchess of Cambridge."

This tradition has been held throughout the royal family with George's dad William and Uncle Harry sporting the shorts as kids too.

Mr Hanson continued, saying:

"The usual custom is that a boy graduates to trousers around eight years old. This is, historically, perhaps due to the practice of 'breaching', which dates back to the sixteenth century. "A newborn boy would be dressed in a gown for their first year or two (these gowns have survived as the modern Christening robe) and then he was breached' and wore articles of clothing that more resembled shorts or trousers than dresses."

He added, "The modern habit of upper-class families choosing to dress their boys in shorts will deliberately hark back to a bygone age. The British upper set are always keen to hold on to tradition, and this one also silently marks them out from 'the rest'."