This is bizarre. Have you never made a fuss of them on their birthday? Surely for people whose parents/family make birthdays an occasion/celebration, it’s natural to return the sentiments?
My sons have always loved at least saying happy birthday. IME with my own kids and those of friends, the progression just naturally goes:
Other parent/family member buys a card. Small child scribbles in it.
Other parent buys card. Child
writes in it.
Other parent may or may not buy small present for child to give to Birthday person.
Other parent reminds child to get card for birthday person. Gives them the money if necessary “Don’t forget its mums birthday on Saturday. Pop into the Spar on your way home from school and get her a card”.
And so on until child is old enough to buy presents for others himself.
My younger son in particular was so excited this year when he chose, ordered and bought birthday and Xmas pressies for family for the first time with his own money.
I mean if you’ve never done birthdays in your house at all it’s different but surely if your children have always enjoyed their own birthdays it’s natural that they want to return the favour - to make someone else happy like you’ve made them?
Really peculiar and cold 🤷♀️