Because QoT is meant to be played like a selfish biatch, it just happens that she can also be incorrectly used as a team player, like Sedna. I'd speculate that it was a limitation of the developer's diligence that allowed her to shield friendly allies not in her personal army.
I know you aren't entirely serious, but there is much truth to it. QoT is much more egotistic, especially your build. Well, maybe Cow's weak-ass shield QoT is even more selfish People actually told me horrible legends about CowbuttQoT: for example, they claim he announces at the very start of the match he won't shield them, won't buy cit upgrades, won't share a lane, etc.
Someone should make a mod script that messages this automatically to teammates at the start of the match, I would pay money for this. 
If you read past posts I am of the same mind set.
Thought images while I am playing QoT
*Shied Minotaur Idol* I am not doing this because I care about you.... you are simply a more efficient mine sweeper or can draw more tower fire this way before you die.
*Shield teammate about to die* damnit, good help is so hard to find [sigh of derision] What would you do without me chuckle head. (coincidentally, this is even more hilarious with my 1 point in shield build because they don't expect the shield to buckle so quickly, I get comments on this all the time)
*Shield teammate drawing tower fire while I spike and annihilate it* In the year 20xx of our LORD, QoT went hence forth to annihilate the tower that was an affront to her glorious, awe inspiring presence.... oh, and player X came along to feel like they made a contribution to removing said tower.
