in the case of said slow mangas, it's not a matter of being made... many of them are even finished on japan... the problem is that these are usually not well know and so the scanlators either don't bother taking them or take them to translate only when they have nothing else to do... which is a shame since some of them are way better than many famous mangas...
and well... our good old azuregos and cyanigosa have purple eyes...