[@DarkFey]There's probably a few reason for this, firstly and mainly, you've got to remember that Quarians aren't exactly well off, they don't have factories or anything on a large scale in terms of production given their ship bound way of life, heavy metal plating in the ME universe has limited uses on foot soldiers, especially for a race that isn't exactly physically adept- any metal plating they've bought or acquired would be used on their ships as it would serve a larger and greater purpose than protecting one soldier.

So yeah, that's probably why- they do look sick though those suits.