For many years, the only two reasons I could think to give my kids for saying thank you were:
- It's polite, and
- It can lead people to do more nice things for you in the future.
Both are true, of course, but an even more basic reason to say thank you is this: It will make you happier.
Gratitude is one of the key components of happiness, after all. To think about what you can honestly say thank you for is to think about the gifts you have received, and not take them for granted.
Expressing an honest thank you is a gift to the other person as well. It helps them realize the impact of their words and actions. It reminds them that what they do matters. And it gives them the opportunity to say "you're welcome," and be reminded of their own good intentions.
To give an authentic thank you is both humbling and empowering. It is a reminder that other people are important to you, and that you have something of value to offer them, too.
I don't think kids -- or any of us -- need to be browbeaten into saying thank you. We just need to be reminded of how good it feels, and how many opportunities there are to do it.