Why can’t we use Wi-Fi to transfer data between phones as we can Bluetooth?
The Bluetooth protocol was designed from the start to be peer-to-peer. That is, it is intended to allow devices to talk directly to each other without any existing infrastructure in the area.
By contrast, WiFi was primarily designed with the access point paradigm in mind, where each network is defined by an official authority, like a wireless router, and all clients must connect to that central authority in order to communicate with each other.
WiFi has some features that allow devices to connect without an access point (called ad-hoc networks), but these features are not commonly used because they are inconvenient and insecure. Most mobiles don’t even both to expose such features to the user, even if the underlying hardware supports them.
The new Wi-fi Direct technology is aiming to do just that. And pretty much all our current devices will be compatible.