You're not missing anything, but that doesn't mean this won't be successful. There were tons of ride ordering/sharing apps before Uber; Uber just had the right interface at the right moment. AIM long predated Whatsapp and Skype. These are just a few examples of not-so-original products that became hugely successful because of some very slight twists on relatively old concepts.
Not being original in concept is far from a disqualifier for success. In all but a tiny fraction of cases, "first mover advantage" is a myth. If your goal is rapid, widespread adoption of your product, it's generally better to iterate on something that has proven acceptance by the market.