There is a section in the Greeting Card Store for “New Baby” cards. I don’t know what other types of babies are available. But the “new” reminds us why we are sending the card.
And “Happy Birthday” goes without saying too. The person knows it’s their birthday, and of course you want it to be happy, that’s why you sent a card. While a blank on the face of the map would probably have as much informational value, saying it more often than necessary is precisely the point of the map.
Sometimes we assume that the person we’re engaging with knows exactly what we mean and what we want to express. But this assumption is often wrong and a little redundancy can go a long way.