If all of the AI labs slowed down, they would collectively spend less on compute, and they'd also be able to charge frontier-model prices for a longer time. However, if they all got together in a room and agreed to slow down, that would look like an antitrust conspiracy. It is generally illegal for competitors to get together and agree to limit the output of their industry. If they all published papers about how important it is to slow down, and the government believes those papers, it might help them coordinate.