The problem is that planes, afaik, do not continuously broadcast their position and health. If you don’t find the black boxes, you can’t figure out what happened. The investigators of MH370 were so desperate for any information of the possible flight path, they had to turn to the pings the jet engines sent to the manufacturer as part of their monitoring [1]. All we need is for passenger planes to broadcast regularly and in short intervals. No indiscriminate high-resolution global monitoring and data processing needed.
[1] https://blogs.crikey.com.au/planetalking/2014/03/25/mh370-la...