The happy couple doesn't write the announcements, a New York Times reporter does. They are much different than the announcements that appear in smaller, more local newspapers and are written more as news stories. Past marriages, whether ended by divorce or death, are considered relevant information. Think of it more like when a celebrity gets married and there's usually a mention of previous marriages (and often to whom) in the news stories about it.
When I submitted my wedding announcement to the Washington Post (admittedly years ago), I wrote what we wanted to say but the Post reserved the write to edit it. No one from the Post interviewed me about the details, and our announcement was very traditional with name of our parents, names of grandparents, where we went to school, and where were employed.
A few years ago, the New York Times ran a story about a woman who wanted the wedding announcement from her very short first marriage deleted from its website because it was the first thing that prospective dates would find online if they googled here. The Times' position is that these announcements are part of the public record and wouldn't delete it. She ended having to create a LinkedIn profile, websites for her businesses, personal websites, Facebook, Twitter, and so forth to eventually get the announcement to stop showing up in the first page of search results for herself.