Thank you and 'bread and butter' letters

I was listening to a discussion on the radio today – essentially, it was saying how few people bothered to say thank you for Christmas or birthday presents nowadays.  As a child, it was drummed into me that thank you letters should always be written and I am sure that my sisters and I always did so – I am inclined to think that most other children of the 40s, 50s and 60s did so too – maybe you can add your comments on the subject. The other thing that was ‘de rigueur’ was the ‘bread and butter’ letter always written after staying with anyone.