Guild Wars 2

One important: kittening runes doesn’t give more bonuses beyond the first one if you don’t have one of its siblings equipped.

After 4 – 5 months playing GW 2 wrong I discovered today that, in order for runes to work with all their bonuses, you need to have 6 identical runes equipped in your armor set. Sigh.
This was not on the tutorial!!!
Would someone explain me what is the logic behind it? Why can’t each rune provide the described bonus without having to look for its additional 5 evil twins?