No one knew AF447 had crashed until many hours had elapsed. It is true that a last known position was established, and the wreckage was eventually found close to the last known position. But I doubt many people think it is optimal that it crashed around 0200 and ATC started asking questions at 0400.
There are many possible tracks for MH370. These generate an impossibly large search area. Some reasonable assumptions have been made, which mean the search area is reduced to merely "enormous."
We don't have the option of rapidly improving inderwater search capability.
We do have the option to track aircraft should we so desire. Or the option to not bother.