NATIONAL ANTHEM

Hi
Befolre you start I was a membr of the forces of the UK.
Why has (or it is not played) Britain not got a National anthem only an anthem for one family and not a nation. There are unfortunately people who do not believe in the royals and because of this anthem to them and NOT the country they have no loyalty to them as they think that they represent all of the people of this country??? :confused::confused: