It's like going treasure-hunting and demonstrating to everyone's satisfaction that there is definitely no treasure where you looked. It doesn't tell you very much about 1) if the treasure you're hunting really exists (there's many more places it could be), or 2) what exactly the treasure consists of.

It's technically more information, but it's not very much information.

eg, what did we learn from the underwater hunt for MH370? not a lot, millions were spent to still have no clue where the thing is. It's not just political to say that the hunt failed in an important way.