Well apart from the massive financial gain the country enjoys from there being a monarchy
Amongst many reasons I enjoy the existance of a constitutional monarchy is I dont want to live in a republic with a president such as say Thatcher,Corbyn, Trump,Putin,Xi,Bolsonaro etc etc etc etc etc etc
I also feel secure in a system that has with odd exceptions effectively functioned for thousands of years ...and when got rid it was soon reinstated,