Probably to make you build more ships for naval battles. 

Not sure about armour (arrows can be designed specifically to work against chainmail, but afaik not against plate) but shields are good against pierce - which is another way to make units differents.

Why has this been removed ?

I'm actually one of the first who understood what you're trying to introduce to the game. That's why I've reacted the way I did. I'm sure the developers understood, as well. Your incoherent, strawman analogies and personal insults have prolonged the discussion and pushed it on to a different path.  It's good that you're acknowledging this. There's nothing more to add, honestly. 

All infantry types used to increase ship firepower before Release 28, not just archers.