Because countries like The UK, The Netherlands etc think it's good for them to have kings. It's not up to Americans to tell the British what government they should have.
Of course, I know the answer and that is because people fawn over the concept and believe that a king or queen is somehow devine or God given.
That is not the reason in England.
Also, the fact that is took a 4 year war to rid ourselves of the king of england is the real answer of why there are still kings and queens in the world.
Nope. The English King was not an American King. He was essentially a foreign ruler.
It takes guts for a population to rid themselves of such a form of government and it gets harder when there is a sweet little old lady in that position as with the UK.
It takes the will of the people. The Queen is more popular than the British Prime Minister. And the Prime Minister was elected. And Queen was not.
An election can mean that half the country hates you. Sometimes more than half, since there are more than two parties in Britain, and it happens that someone whose party gets fewer popular votes can win more seats in Parliament and make you PM. And, of course, Britons don't vote for the PM directly, though even if they did, he'd still have his opponents.
I suppose the British think that getting rid of the monarchy would leave a large vacuum in their culture and take away a stabilizing influence in their politics. Also, it's good for tourism.