If somebody is willing to you a favor it is only natural to want to return the favor. However, some forsake the moral obligation and pretend not to have enjoyed any benefits they might have received. Others may just think they have done everything they should after repaying a debt to some minor extent as they see fit. Others feel thankful inwardly, but they don't express their gratitude with words or deeds. But men of good heart never forget the benefit they've received and their hearts never change.
"What shall I render to the LORD for all His benefits toward me?" (Psalm 116:12)