He does rush the passer sometimes out of that formation. Sometimes they'll use him as a spy or send him on a delayed blitz, but he rushes straight sometimes too.
I think the problem with him is that he's a bit of a one trick pony with his speed rush and doesn't have the size to fight through a block once a lineman gets his hands on him. So basically they have to try to find ways to use him where he can zoom by a blocker with little chance of being taken completely out of the play.
Using him as a spy or on delayed blitzes are the easiest way to do that. If our other guys were doing a better job of disrupting the pocket, it would probably be much more effective.