Because she brings nothing to the ticket.
Worse yet is what she brings to the ticket. She is the wrong gender.
1. Said Cruz would say or do anything to get elected
2. In desperation move, Cruz names her his running mate
3. Oops. Watch that first step, it’s a doozy https://www.youtube.com/watch?v=ezJpN_CaDhE
4. The great Cruz-Fiorina ticket lasts a week.