Bluetooth is slow. The transport is 3Mbps at max, if you subtract all the headers from different layers, you may have like 1.5-2Mbps practical transfer speed.
replySounds like the "or such" wins, but even with bluetooth speeds that means you're backing up 1-5 photos per minute and that helps a lot.
replyAnd harm a lot too, you phone can't deep sleep since it has to wake up periodically to process data from bluetooth stack. Combined with slow transfer speed, that gonna eat your battery like nothing.
replyPlaying audio over bluetooth also wakes things periodically, but it uses almost no power. With a similarly competent design photo transfer should be very battery efficient.
replyThey do transfer, but it's not automatic.
replyMy Nikon ZF transfers to my phone through Nikon's SnapBridge app automatically.
replyOh, that's cool, kudos to Nikon, could be a good reason to switch over from Fuji.
replyWiFi is a little faster I guess? In the primitive days people used the EyeFi.
replyYou would often not have wifi available, and you wouldn't want to have to type in wifi passwords to your camera all the time. But your phone will almost always be nearby and persistent bluetooth is easy.
replyWifi between your camera and the phone. Or your camera and a laptop in your bag or whatever...
replyProblem is they have to disconnect from the current wifi ap to connect to the cameras ap which is inconvenient and means there can’t be a constant connection.
replyWifi NAN could be used to solve this problem but I’ve not seen anything using it. Apple only just added support last year though.