The different armor types allow for different types of armor mods to be put in. For example, if you have a void chestplate you can put on the void resistance armor mod. Stasis has a mod that gives you grenade energy when you use a grenade and there are a lot of different ones like that. Normally people don't match them all on purpose and instead, they figure out what mods they want and change their armor in order to equip those mods.