I think thank you cards are a downside for everyone.
In general, so many wonderful things happen that it's hard to thank everyone. I was once bumped on a plane and the next plane going where I was didn't leave for 48 hours. So I stayed at a friends' parents home. And they were so welcoming and hospitable, even at the last minute.
But when I got home, I forgot to send them a thank you card. It wasn't until a few years later, when I saw them again, that I remembered that I still had not sent a card. So at that point, I just sent them a thank you/ thinking about you card referencing that weekend and letting them know that I still appreciated their kindness.