Requiring WiFi makes (so the phone/computer is on a network and can communicate with the other devices), but what's the benefit of Bluetooth? Does it only work when the phone and computer are near each other?
Bluetooth is used to discover peers and to initiate communication. Thus handoff works even on a wifi network that blocks broadcasts. It even works when no wifi network is present, by setting up an ad hoc network for the connection. (Disclaimer: This is all I know. The details seem rather murky, as handoff is a proprietary Apple protocol.)
