You are supposed to put pics on the OP.
Anyway...
People do use it. FG Decks, against PC-heavy gods. To protect that one Eternity or the Sanctuary.
Or Dim Shield + PA? Now that's scary.
Reason why:
1. You usually have reserves anyway
2. That one slot could be used to pack more damage
It is balanced as it is. People just rarely use it because of its defensive nature. Same reason why Warden / Diss Shield are rarely used.
And balancing does not take into account the card popularity (except if people don't use it because it's weak, that's another story), only card power counts.