Facebook/ social media announcements

Excuse me if I'm wrong but i just don't understand the need to announce on a social media platform that you're pregnant. I really don't understand the concept. What is the actual purpose? To show all your friends that you used to speak to how great your life is. If you want people to know, pick up the phone and speak to them or meet with them in person. I just don't understand. Don't get me wrong I've annouced that I'm engaged, married etc etc but looking back who was it really for? pregnancy is so volatile, so many things can go wrong that it seems to risky to announce something so personal. I've just noticed this obsession with announcing you're pregnant with creative little pictures. Why not try and keep something private and personal. Because the only people who care in the end is you and you're partner and your families. End rant.