I thought the "they don't know you" argument was much better than the "you're not royal" one.
Canadians were all going "What the heck is Ben Mulroney doing in the front row, he's sitting closer than the Queen!". It's because he and his wife know Megan Markel very well. Their kids were in the wedding party; it was his son who had the big grin when he heard the trumpets.