Why do airplanes still use a "black box" to record flight/voice data when they could just send the data in real time to satelites.?

This question has been debated for some time. Problem is that you can't keep a satellite uplink open full time, it jams a whole transponder for you only, and there are not enough transponders, so the cockpit audio would be sent in packets, and unless the accident happened just after the last packet was sent, you would always lose the last bit, which is usually the most interesting bit.

Also, it would be objected to by pilot's unions, because it would enable employers to listen in to cockpit conversations in real time. The present system includes a button which can be pressed to erase the recording, so if two pilots spend ten minutes discussing the sexual preferences of the chief pilot, they can press the button and erase the record.

Also, satellite communication is often difficult or impossible, especially at high latitudes using conformal antennas when flying north or south.