>>212349415French vocabulary functions a little bit differently because it's been part of the language for so long. Loanwords introduced directly from Latin and the other classical languages in the early modern period tend to maintain many of the morphological characteristics they had in the languages from which they were derived, especially those pertaining to number. The same is also true of words adopted from other languages today. It's apples and oranges. We don't say mangas, animes, doujins, bishoujos, otokonokos or otakus. It's just common sense.