#need to keep an eye on how people sweeten their tea

Headcanon: Metheglin is Setheris’s plonk of choice because honey remained the Ethuveraz’s staple sweetener well after they’d reached the cultural/technological point when comparable societies in western Europe had access to affordable sugar.  And that makes sense considering that Ethuveraz seems to have expanded as an empire by pushing out from its old borders rather than going overseas (so no equivalent to Britain/France/Spain’s Caribbean colonies), and the parts of the Elflands that have shown up in the books so far appear to be much too cold to grow sugarcane.

(Assuming a roughly 19th century tech level, they could certainly grow and process their own beet sugar, but that would probably be a fairly recent innovation.)