Because no one with enough money is dumb enough to believe there is any merit to these claims. We rewrite history all the time... It's encouraged by the US government. Millions of dollars in grant money flow to colleges around the US for just such investigation.
The Gov't hides new planes, immoral practices, and information to protect their own butt... Not random underwater formations that may or may not be anything.
They KNEW the Titanic had valuables in it. It was less risk. There is very little chance of even a piece of gold being found even if this turns out to be a sunken city (which I doubt).
Something is not right. This message is just to keep things from messing up down the road