This question already has an answer here:
Now that the Malaysian flight was again in the news, that they had officially given up and stopped searching, this issue comes to mind again.
Why do w all depend on finding a physical recorder, and why is it so hard to find?
Why isn't the system updated so that the flight recorder can live stream all its info back to the manufacturer?
Why does it only give off sonar signals and not high frequency electromagnetic broadcasts which, I would imagine, would be far easier to find?