Its because they've really got nothing else to offer. Between punk being out, ziggler being injured and how badly they've neglected so many superstars there is just no one else they can use as main eventers.
When the Devil is to busy
And Death's a bit to much
They call on me by name you see, for my special touch
To the gentleman I'm Ms. Forture
To the ladies I'm Sir Prize
But call me by any name, any way it's all the same