According to WhatsApp:
We’re introducing this feature because we know that sometimes voice and text just aren’t enough. There’s no substitute for watching your grandchild take her first steps, or seeing your daughter’s face while she’s studying abroad. And we want to make these features available to everyone, not just those who can afford the most expensive new phones or live in countries with the best cellular networks.
Over the years we’ve received many requests from our users for video calling, and we’re excited to finally offer this feature to the world. Thank you for using WhatsApp and we promise to keep working hard every day to improve the service.
WhatsApp’s goal has always been to help as many people as possible stay in touch with friends, family, and others they care about. That means making a product that’s simple, easy to use, and accessible no matter where you are. The company started with messaging and Group Chat, then added voice calling, in a way that works across thousands of device and platform combinations all over the world.