Surely it all depends on your family dynamic?
My child will get her stepmother a card, because stepmother will want that, and will make sure she tells her husband (my ex, child’s dad) to make it happen. My child will also be happy with that, though it won’t be spontaneous.
At the same time, my child won’t get me, her actual mother, a card - because in this house, we don’t believe in random days to show appreciation. It’s not our thing.
My own stepchildren won’t get me a card. I wouldn’t find it out if they did, but their mum is dead, so I think getting one for me would highlight the fact their own mum won’t get one. So for our family, it just isn’t the right thing to do.
As a stepparent, I’d say - sweet if they do, not a problem if they don’t.