Why doesn't Captain Ahab meet the sailors?

Ishmael is told that he cannot meet the Captain because he has shut himself up and wants to be alone.

"But I don't think thou wilt be able to at present. I don't know exactly what's the matter with him; but he keeps close inside the house; a sort of sick, and yet he don't look so. In fact, he ain't sick; but no, he isn't well either. Any how, young man, he won't always see me, so I don't suppose he will thee. He's a queer man, Captain Ahab—so some think—but a good one."