If a volcano decides to rise from the seabed there isnt a damned thing we can do about it except warn that the water is on the way. Why spnd a ton of money on it, fact is Yellowstone Park could produce a volcano tomorrow and cover half the earth with ash. Nothing we can do about it.
I think that is the point. If you monitor, you can then warn.
With the recent tsunami, just being inland as little as a quarter mile would have meant the difference between life and death.