There were two apparent reasons, for Alice Deringham realized that there was a certain greatness behind his simplicity.

Granting that, she could see his standpoint clearly, though it was more difficult to understand why such a man had made it evident to her.

He was, she knew, not one to stoop even to win a woman's good opinion, and would have seen that in this direction silence became him best, unless he felt that while so much was due to honour there was something due to her.
He had told her simply that it was not to please himself he was going out to look for the silver just then, and the deduction was that the expedition had no attractions for him because he wished to stay at the ranch.

Allowing that, the revelation of his motive had not been purposeless.

It was only his responsibility drove him away from her, and there was a vague but effective compliment in the implication that she would recognize it.