Congratulations with the grandbaby. Lately I went to two weddings of friends. One was a pharmacist and the other was
a business person -I never got thank you notes from either of them. Their parents sent me birth announcements of the babies they had. I decided not to send them baby gifts. I'm sure the birth announcements were meant for me to send gifts.
Also another friend's son who has a phd and teaches at a university they sent me his birth announcement and I sent them a gift and they did not send me a thank you note. I don't think the younger generation has thank you understood.And from what I see there financial level or educational level does not affect their understanding of a simple thank you.
With my difficult child I restrict him of privileges until he writes his thank you notes and it is a big deal to get it done. I think if he were out of my house it would be impossible.