"Unwillingly Jack answered." Why unwillingly?

I think Jack just doesn't like to answer to Ralph. Jack thinks it makes him look weak.

Now think, Jack. Is there anywhere on the island you haven’t been?”

Unwillingly Jack answered.

“There’s only—but of course! You remember? The tail-end part, where the rocks are all piled up. I’ve been near there. The rock makes a sort of bridge. There’s only one way up.”