Analyzing the causes of plane crashes saves lots of lives. You can't do that with a disappeared plane.
And recovery is only possible if you can find the wreckage. MH370 is still missing, and as such the cause of its crash is unknown. If we had real-time GPS monitoring of airliners, chances are we'd have wreckage in-hand.
17 unrecovered black boxes since 1965. I don't think that calls for spending tens of millions of dollars considering ADS-B and Iridium will have the problem solved in the next few years: http://www.aireon.com/AboutAireon/AnIridiumInnovation
Anyway, 6 minutes (not 16) is the time people are usually expected to still be alive in a plane after it gets on fire. Airports spend a lot to get cars on their area fast enough for rescue, there's simple no chance boats can get anywhere in the oceans that fast - when a plane falls on the water boats need days to get there. And all "the nearest boat" will do is catching fire together with the plane, you need well equipped boats with trained people.
Anyway, I'm having a hard time trying to imagine a scenario where airplane tracking fails, but people are still alive. I'm about to claim that's currently impossible, but that'd be just asking for a counterexample to happen and prove me wrong... When planes disappear, it's because they were either completely destroyed in air or hit the ocean at a huge speed.
A low priority, but not nothing.
That said, good telemetry brings economical gains. Planes will stop disappearing in due time, just not by state decree, and probably because of more usfull devices than this one.