Because often--- elite prospects being broken in as MLB closers as opposed to as SP doesn't really work out when the team decides to convert them to a starter.

And, Neftali Feliz- Stud Closer sounds WAY better than Neftali Feliz- Stud SP, in terms of future damage done.

(yes, he was in the bullpen before being made the closer, but I'd love if he settles into that "closer" role)