I imagine it is the fact that it hasn't been an issue until very recently. And with anything aviation it takes forever get to developed, approved and then actually purchased and installed. A whole lot goes into that process.

But they still found the boxes of AF447, MH307 is a missing 777 that alone is just mind boggling, and they found this one relatively fast. So it still works, the data is almost always good no matter how bad the crash, so there is a lot to be said for that.