There is something very personal about receiving physical cards over digital ones. With physical cards, being able to see someone's thoughts in their own handwriting feels more intimate. Unfortunately, with the present digital age, physical cards are becoming more rare. With invitation cards in particular, it can be more convenient to send them digitally for rsvp purposes.
We have decided in our home to always give cards to any of our friends or family members during Christmas or other celebrations. At least this could help my children grow up with this tradition.
This will also be a great way to bond with your kids. If you have any on the younger side and can't write yet, you can provide them with stickers to help decorate the cards.