The invitation now has a second job
For a long time the wedding invitation did exactly one thing: it asked. The asking was beautiful, then it sat on a shelf and you chased the answer by telephone for a month. An online invitation keeps the asking and quietly takes on the other half, the part nobody enjoys, which is collecting who is coming and who they are bringing.
This matters because a modern guest has more questions than a card can hold. Which church, and is it the same building as dinner. What time to arrive, given the photographs beforehand. Whether the children are invited or the day is adults. A link answers all of it in the same calm voice as the invitation, and then offers a plain button to reply, so a yes arrives as a tidy record rather than a message you decode over breakfast.