I think questions like this SHOULD be asked, and asked loudly after two international airliners have been lost at sea. The chance that any people may have survived the contact with water are very low indeed, but still it is possible to imagine a few miraculous survivals who might have been saved if the aviation industry knew where its planes were and what was happening to them.
I know that money, testing, certification etc are all huge factors, but nonetheless the improvements in airframes, engines electronics etc. over the last 2-3 decades seem NOT to have been matched by improvements in tracking and monitoring, and this has to be addressed.