It is polite to thank others.
John and his Wife Andi are dining when John is given a watch by his wife for their fifteenth wedding anniversary.
John wants to respond to the gift.
John tells Andi that it's wonderful and thanks her for going through the trouble of getting the gift.
John tells Andi that the watch isn't quite the type he likes and that he'll probably end up returning or exchanging it.
Andi is happy John is appreciative and is glad hat he likes what she has chosen for him.
Andi feels sad that John doesn't like her gift and feels like she must have done something wrong.