There are a lot of things that parents did not teach kids. In fact, just ask any kid or adult: if they want to do something and they don't know how to do it, the fact that their parents did not teach them will not stop them from learning how to do it. So, it is no excuse if parents did not teach them to write thank you notes. If they wanted to say thank you, they could find the technology to do it. They certainly find the technology to write everything else. If someone if ungrateful, then that is just an ungrateful person regardless of however they excuse it as being forgetful or too busy, etc. We only have 1 GD out of 7 who has said thank you and we had to pay for part of her college to get that!