Yes, it clearly started out at least partly as a prestige thing. Books (and even periodicals) indeed used to often have the publication date in Roman numerals,

Yes, it clearly started out at least partly as a prestige thing. Books (and even periodicals) indeed used to often have the publication date in Roman numerals, and the older and more self-consciously presteegious a book is the more likely it is to have them in that format. Clearly the inter-war studios were trying to claim some of that prestige for themselves, just as they added other neo-Classical elements to their branding for similar reasons: think of the Columbia logo and so on. (BBC TV credits use Roman numerals as well. Apparently they switched from Arabic to Roman as late as 1976: https://www.tvforum.co.uk/tvhome/bbc-colour-end-credits-change-31508 https://www.tvforum.co.uk/tvhome/bbc-colour-end-credits-chan... )