Oh, they cared, and they tried, but it didn't work out like they intended. And now Harmonix is moving on from Rock Band so it's not a problem they are going to put any effort into fixing at this point. Disappointing, sure, but these things happen. Obviously the job of balancing the power-ups is not as simple as it appears. It was unbalanced before (Flame Notes) and it's unbalanced now (Pinball).
I keep trying for the random participation prizes but haven't gotten lucky yet.