That's because people tend to be fooled into thinking the tween market is bigger/more important than it actually is due to how vocal the demographic is traditionally. Tweens usually dominate social media and music blogs, so you get the impression these tween acts are bigger deals than they are.
But all you have to do is look at who the highest album sellers and tour grossers are to know that tween-focused acts really aren't calling the shots.
Heck, the same can be said about One Direction. You'd think they were the biggest thing since sliced bread if you only followed social media and ONTD, but in reality their album sales aren't that great and their second single is a flop (in the US. Not sure about everywhere else).