Unrelated to this post but what does it mean when a person isn't invited to the whole day?
More commonly though, I've been to weddings where they had a small private ceremony (just the couple, officiant, and a handful of family), and then a large reception for everyone in the evening.
It’s therefore not uncommon if it’s local for more distant friends of family, neighbours, etc. to pop along to the ceremony at invitation of the couple or their parents as a result, but not to be invited to the party part. Sometimes older guests will just come to ceremony too.
That's an insane legal requirement. I'll do the legal wedding in the most unceremonious, quickest manner possible, and then have my real ceremony in privacy and not tell anyone about it.