Not good way for sending bitcoin using bluetooth because only can make transaction with close mobile phone device, how ever bitcoin is digital currency payment transaction where could send for other country with have far way each other, if keep using bluetooth as way for sending make bitcoin become down as legal currency payment transaction.
Do you never give money to your friends? It could be convenient when the person is near you. If you need $10 you can ask your friend to give you $10 and you give him the equivalent in Bitcoin. "Hey dude, give me $10 if you can, I give you 0.001
BTC in exchange, turn on your BT connection".
Not everyone has an internet connection on the phone. Internet here, internet there, we're always connected to the internet in a way or another, always living near a connected device. At home, at work, at the train station, at Mc Donald, everywhere, even in the toilets. Sometimes it's boring.
No need to use Bitcoin only to send money via the internet to someone living far away from you. Bluetooth is energy-saving also, it even uses less than Zwave, Zigbee protocol. Yes, the distance between Wifi and Bluetooth isn't the same but we don't care, you don't talk to a friend at 100 meters from you "Hey dude! How are U? Do you hear me? I send you the 10$ from last week!"