T–V distinction
In the public situations in which it is used, the monarch or other dignitary is typically speaking not only in their own personal capacity but also in an official capacity as leader of a nation or institution. In the grammar of several languages, plural forms tend to be perceived as deferential and more polite than singular forms. This grammatical feature is common in languages that have the T–V distinction. English used to have this feature but lost it over time, largely by the end of the 17th century.