What's the point for an airline to receive in real time the data concerning engine thrust, rudder movement and so one. This is of no use to the company which expects its aircraft to land safely on every journey.
Yes, when crashes like that happen, we would need this data, but it does not justify implementing on every aircraft live DFDR data transmission. Besides, many A/C do not operate ETOPS flight and remain isolated from the rest of the world for substantial period of time.
Finally, Airliners would have to modify their installations to cope with all these data.