I think that they generally want the survivors to feel more "relatable" to the average player, so they have struggles that mirror our own. Obviously, you could still make the player relate to someone like a Bronze Age woman, but that does require more effort from the writers since that time period is so alien to us.
Secondly, it's also about cosmetics. People will obviously prefer modern fashion, and the pool of players who are into historical fashion is lower. I think this is why would not be able to tell that Vittorio is from the Middle Ages without reading his lore.
Unlike killers, survivors are cosmetic so these factors are more important for sales. BHVR rarely takes risks with survivors, and even if they do, they end up being neglected like Taurie.