>>530571980
The demon names are supposed to be the various characters' 'real' names, it's not necessarily limited to just the shades and archons (and Paimon) since there have been the occasional jobber god who also has a name from Ars Goetia
The names aren't really titles or something similar bestowed upon them and although it's a rather boring answer it's most likely just a case of being a reference for the sake of being a reference or simply because the names sound cool