Land a lot of places that a Herc can't. There's a book out on the C-27 by a guy who flew them in Panama, and while he takes liberties the fact is the C-27 needs a lot less room to do its thing. And I, too, hated flying half a cargo load of twinkies when a smaller plane could have done it.
That said, a plane only makes sense if you can pay for it. The Herc can get 90% of the jobs done 90% of the time, so we don't need a luxury twin-engine weighing on the budget.