Okay, I admit I didn't read the actual question or passage because I felt like I didn't have to to answer your question, which is generic. Forming and breaking interactions with other proteins is important to any signal cascade because signal molecules are usually "catalytic." What I mean is that one signal molecule will activate a protein, then unbind, and go activate another protein. Signal amplification is one of the key tenets of a signaling cascade and that's what this provides. If your signal molecule sticks to a protein and doesn't let go easily, then you need 1 signaling molecule per protein molecule you want to activate. That's hardly a cascade. But if your molecule hits the protein and immediately flips the on switch and then immediately dissociates from it to go find another protein, then you have a cascade in the making.
