I suppose what I'm trying to say is that you can still be thankful even if you don't say or write the actual words "thank you".
If I hold a door open for somebody, and they smile, I know they are thankful, even if they don't say it. Why would anybody NOT be thankful for someone holding a door open? "I wish that bitch would have let the door slam on my face." I don't need a pat on the back, or for someone to tell me how I'm a good girl for doing it. That's not why I did it.
There are drivers who will expect pedestrians to say thanks if they stop at a zebra crossing. Thanks for what, not running me over?
There was a similar thread the other week, where the OP thought the person on the check out at the supermarket was rude because they hadn't said please when telling her how much the shopping would cost.
Manners and rudeness don't begin and end with the words please and thank you.
Back to the matter in hand, I still don't think that a thank you card that a 4 year old has been "made" to write is truly sent with gratitude. I'd rather have no thanks than a forced thanks.
Once again, nice to receive them, but not the end of the world if I don't. I probably wouldn't even notice.