Many years ago, in the world all the country have the Royal.
Ok, it’s in addition to the United States.
But nowadays, the Britain’s system of government is different from the other countries.
For example,
Many years ago, there have the Royal in China.
And the emperors ruled China about 5,000 years of history.
But nowadays, who has the Royal lineage, we don’t know.
Nowadays, in UK. The present monarch, Elizabeth II, has reigned since 6 February 1952.
“She and her immediate family undertake various official, ceremonial and representational duties.
As a constitutional monarch, the Queen is limited to non-partisan functions such as bestowing honors, dissolving Parliament and appointing the Prime Minister.”
From (Wikipedia)
I think the Queen and the Royal is tradition or culture.
They don’t have any political rights.
But now, they have become an indispensable symbol of the UK.
Nowadays, the UK has the royal family.
It’s must be some reasons.
So, I think, the royal family is an integral part of the UK.
And there have some picture to prove my point.
It has been integrated into all aspects of the UK.