I mean maybe some people did dual wield, and they also probably died first. Why give up a shield for another weapon, you will get shot or poked by a spear before you even have the chance to swing it anyways.
Its good that the series has a lot of axes, instead of swords, but the lack of spears is still sad. Spears were pretty much the best weapon to have back then. Cheap to make, penetrates armour and can be used at a distance, just a allround effective weapon.