When did thank you notes go out of style?

I'm a big believer in thank you notes. Not by e-mail, not even with a phone call. But a handwritten, 39-cent-stamped thank you note (hand delivered works, too). There's nothing nicer than receiving a handwritten note -- and not just for gifts. But for someone doing something nice for you. For someone's hospitality. For hosting the family at the holidays for dinner.

I had my 13-year-old niece stay with me last month. An overnight stay -- I bought her lunch at a restaurant, paid for our activities. She thanked me when I brought her home the next day -- but it bothers me that I didn't get a thank you note from her. She's old enough to be able to do it on her own. And most people in my family are thank you note writers, so she's had experience with them. Knows what it's like to receive them.

Maybe she (and her parents) don't see the importance in them. Maybe the verbal thank you was enough in her mind. I feel bad that I still haven't sent all my thank you notes to the people I stayed with in Baltimore.

There was a time when thank you notes were an automatic. When did that change? And am I the only one this bothers?