there is negotiation there, your actions speak instead of you. There are tenuous differences between moves which do speak for those who can hear them.
Gunboat is far more strategy, than full press, but it is not pure strategy. The way you abandon places, the decisions you make who to ally with are part of your negotiations.
Surely until you haven't played a gunboat over 3500-7000 pot size it is hard to understand, but those guys do. Recently we have invited a few new players into those games, like anlari, and Draugnar, though Draug's game is still going on. However anlari could share his experiences I guess.
So anyone who underestimates gunboats simply doesn't understand the metacommunication among players. But by time you can learn, moreover enjoy it. I am extremely curious what will Draugnar say after we finish his game.
For me, personally, gunboat is a ballet, a beautiful coreography of silent dancers who tell you a story of how one of them has arisen while others have fallen. A symphony without instruments, though you see the musicians play. And if you listen carefully, suddenly you will be enlightened whats happening there, what they "say" to eachother publicly, as everyone can see it, yet only a few understands.