@Demiller,
You are missing the point. Once
you were the grandchild disappointing your grandparents. Now you are the grandparent being disappointed by your grandchildren. Grandparents have always been complaining that their grandchildren are spoiled, this was as true when you were a child as it is today. This has been the cycle since at least the time of Socrates.
The way you feel about your grand children is no different than the way your grandparents felt about you. They didn't understand how you thought, and your behavior confused and sometimes disappointed them. Hopefully they still reached out to be understanding and have a relationship with you as a child.
Your grandparents failed to change your behavior (or you would never vote, and always wear a pinafore). You will fail to change the behavior of the kids today. And the world will continue to progress in spite of the best efforts of grandparents who want it to stay the same.
You say that "anyone would like to receive a note of gratitude". I am not sure that this is the case. Culture has changed, whether we grandparents accept that or not. Culture is always changing. You can ask them... it might be that honestly they don't care about this formality and that is the reason they don't understand it is important to you.
We can accept that, or we can resist it. But if you want a meaningful relationship with your grandchildren, you have to reach out to them on their terms. Of course you can communicate with them, give them advice and tell them that you like thank you notes.
But that's all we old people can do. The world goes on in spite of us.