They don’t.But how do Earl's get to outrank Kings and Queens by anyone's standards?
Other than - wait for it - the aristocracy are quite snobbish. And make up their own social conventions to mark out parvenus within their own peer group. Hence the Windsors are seen as a bit déclassé, hence an Earl of Dartmouth is someone you dump and divorce for an Earl Spencer so you can hold your head higher, hence a 14th generation title is great while a 2nd generation variety is barely more than a Mr.