The case for a printed card is real: it is lovely, it is tactile, some relatives genuinely prefer it. The trouble is what happens after it is opened. The registry note is on the back and gets folded away. The date is in the kitchen drawer. The address changes, and only the people you phone hear about it.
A digital baby shower invitation keeps the details attached to the page they describe. One hosted page holds the date, the address, the theme, and a link to the registry, and it carries a reply button so each yes lands on your guest list rather than lost in a group chat between food photos. When something changes, you edit the page and everyone who opens it next sees the truth.