I've said it before and I'll say it again. Our generation does feel hurt at not receiving thank-you letters, Christmas and birthday cards etc.
If we brought up our children to write thank-you letters, we have good reason to be hurt, if not, we can blame ourselves for their lack of manners.
Assuming that we all did teach good manners to our children, try not to feel hurt. You are only distressing yourself.
Our children's generation feel thank-you letters are a thing of the past. We can't change that, however little we may like it.
Inconsiderate? We think so, but they don't.
In the 1970's we stopped wearing hats and gloves on formal occasions, I quarrelled with my mother because I didn't want to wear stockings at dinner in particularly hot weather, and annoyed her by politely contradicting elderly ladies if I didn't agree with their opinions.
My mother had been brought up to never contradict someone older than herself and had tried to pass this on to me. I found it hypocritical to say, "How right you are." to someone I thought was wrong.
Times change and manners change with them.