It’s a different world today. I’m not saying it’s ok to not send thank you’s for gifts. I’m just saying I see this with my adult kids and their grandparents.
Maybe try to think about it differently? ( to help you not to be so upset).
I assume you want to give them gifts? VS feeling “obligated” to give them gifts?
If that’s true, decide if you will continue to give the gifts if some form of “thank you” is not received ie a text, call or card.
Ideas:
If you choose not to send gifts, set aside the funds that you would use to buy them a gift on each occasion in an account or an envelop. Give that money to them at some point that you feel is a good time.
OR
Send them a card in place of gifts: you have remembered them on the occasion but then there is no need for a thank you from them.
I have a feeling you want to give them gifts even if you don’t get a thank you. But I feel since it upsets you terribly, you may need to make some boundaries for your sake.
I’m not aware of you’re proximity to the grandkids? Or if you see them frequently?
I’m not sure why this happens and I know it is thoughtless and hurtful.